BATTAGLIA, J.

Joseph William Payne and Jason Bond were convicted in a joint trial of first degree felony murder and kidnapping, along with the use of a handgun in the commission of a felony. These convictions were based, in part, on the testimony of Detective Brian Edwards of the Baltimore County Police Department. Detective Edwards testified, without having been qualified as an expert witness under Maryland Rule 5-702,1 that by interpreting Payne's and Bond's cell phone records subpoenaed from Sprint Nextel2 for the period from August 26 to August 27, 2007, he was able to determine the location of cell phone towers through which particular calls were routed and to plot the locations of those towers on a map in relation to the crime scene. The attorneys for Payne and Bond objected to Detective Edwards's testimony arguing, inter alia, that he should have been qualified as an expert. The trial judge overruled their objections and opined that Detective Edwards's testimony only related facts that could be independently verified from the phone records.

The trial judge also admitted into evidence against both Payne and Bond six recorded phone conversations in which Bond was a participant but Payne was not, in which the discussions suggested an alibi on the night of the murder. After the trial judge had determined that a conspiracy to conceal the murder existed and that Payne and Bond were participants in that conspiracy, she admitted generally the six recordings.

In a reported opinion, the Court of Special Appeals reversed Payne's and Bond's convictions, ruling that the trial court erred in admitting Detective Edwards's testimony without his having been qualified as an expert witness. Payne & Bond v. State, 211 Md.App. 220, 231, 65 A.3d 154, 160-61 (2013). Thus, a new trial was ordered for both defendants. Concerning an issue likely to arise upon re-trial, the intermediate appellate court apparently determined that Bond's statements during the wiretapped telephone calls could be admitted against Payne, not as the statement of a co-conspirator, but under Maryland Rule 5-803(a)(1),3 which permits admissions of a party-opponent. Id. at 252, 65 A.3d at 172-73. We granted the State's Petition for Certiorari to consider the following question:

We also granted Payne's cross-petition to address the following question:

Payne & Bond v. State, 434 Md. 311, 75 A.3d 317 (2013).

We shall hold that Detective Edwards needed to be qualified as an expert under Maryland Rule 5-702 before being allowed to testify as to his process for determining the communication path of Payne's and Bond's cell phones, as well as his conclusion that the Menlo Drive cell tower and the Balmoral Towers cell tower were the most pertinent to the case.

The present case began when, in the early morning of August 27, 2007, officers of the Baltimore County Police Department, including Detective Brian Edwards, a fourteen year veteran of the force with four and a half years in the homicide unit, responded to a call and discovered a body on fire in the woods at Villa Nova and Queen Anne Roads in Pikesville. Early in the investigation, detectives recovered a scrap of paper from the bedroom of the victim, Glen Stewart, containing two names and associated phone numbers, one of which was that of Desmond Jones. Investigation of Desmond Jones's cell phone records led detectives to identify numbers associated with Payne, Bond, Christopher Johnson, Tyrice McCant and Brittany Keller. Detectives obtained dialed number recorder ("DNR") authorizations to capture the numbers of phones called by those individuals. According to the State in its brief, the "DNRs showed numerous calls between McCant, Keller, Payne, Bond, Johnson, and Jones" around the time of police interviews of McCant and Keller in late October and early November of 2007.

Investigation of Jones's records also led Detective Edwards to subpoena additional sets of "phone records" associated with phone numbers with which Jones communicated, totaling "close to a hundred different sets of records". These "phone records", which were received electronically from Sprint Nextel, totaled "thousands of pages" when printed. Detective Edwards testified that he then chose individuals identifiable as the most "pertinent", including Payne and Bond, for whom he amassed records of their cell phone calls from August 3 through August 31, 2007. Apparently, the amassed information was in the form of Call Detail Records4 for Payne's and Bond's cell phones, which accounted for roughly thirty to forty pages for Payne, while Bond's were "under 10 pages".

Detective Edwards further testified that, once he isolated the separate working copies, he parsed Payne's records to a single page document and Bond's records to a quarter-page exhibit, of trimmed call entries depicting communications to or from Payne's and Bond's phones within the timeframe from August 26 to August 27, 2007, under the headings of "Duration", "Direction", "Dialed", "Beginning Tower", "Ending Tower", "Lat" and "Long"; each document was admitted into evidence as Exhibit 12 and 11B, respectively.5 Excluded from both exhibits was information that Detective Edwards determined was redundant, extraneous,6 as well as identification numbers for the cell towers associated with each entry for which he substituted his own derived geographical coordinates.7

Detective Edwards also testified that he could determine the call time, phone number called, whether the call was incoming or outgoing and the cell tower through which the cell phone communicated, based on the complete records he had received from Sprint Nextel. When Payne's counsel objected to the Detective's testimony on the ground that Detective Edwards needed to be qualified as an expert in order to interpret the data, the State responded that the actual records contained step-by-step instructions as to the use of the records, although neither the actual records nor the instructions were introduced into evidence.8

Detective Edwards proffered, outside of the presence of the jury, the procedure that he used to determine cell tower locations. According to him, the process required matching certain data points associated with a cell phone call to a table available on an unnamed "secure Web site" or on "an Excel spread sheet that comes with the records", to determine the latitude and longitude of the corresponding cell tower.9 Neither the "Excel spread sheet that comes with the records" nor the "secure Web site" that allegedly maintains cell tower information was admitted into evidence. Satisfied that Detective Edwards need not have been qualified as an expert to testify, as he did to that point, the trial judge permitted the State to further question the Detective about the location of the cell towers that transmitted Payne's and Bond's communications listed in Exhibits 12 and 11B.

Detective Edwards testified thereafter regarding the location of the first cell tower to which Bond's cell phone allegedly connected on the night of the crime, a cell tower located on Menlo Drive, and opined that the cell tower was between one and a half to two miles from the crime scene.10 The State then offered, as Exhibit 9, a map Detective Edwards created upon which he had printed what he determined to be the location of the Menlo Drive tower as well as the location of the murder.11 Detective Edwards further testified that he determined Bond's cell phone also registered off of a second cell tower located on the Balmoral Towers building, which, according to him, was located approximately a mile from the crime scene, all of which was reflected on Exhibit 9, which was admitted into evidence.

An oversized aerial photograph, already admitted into evidence as Exhibit 2, of the area surrounding Villa Nova and Queen Anne Roads then was shown to Detective Edwards. Exhibit 2 contained a preprinted graphic showing the location where the victim's body was found and a sticker identifying the home of a witness. The State then asked Detective Edwards to place a sticker depicting the location of the Balmoral Towers cell tower on Exhibit 2, which he did.

The State then presented Exhibit 3 to Detective Edwards, which was another oversized aerial photograph showing, on a larger scale, the same general geographic area depicted on Exhibit 2 and which was admitted into evidence during Detective Edwards's testimony. On Exhibit 3, the State had identified the location where officers found the victim's body, in addition to the location of the residences of the victim, Payne, Bond and two others who had been investigated by police in connection with the murder.12 Detective Edwards, at the State's request, again identified and indicated by stickers the locations of the Menlo Drive cell tower and the Balmoral Towers cell tower on Exhibit 3.

Detective Edwards further testified that, by using the call entries in Exhibit 12 — the edited records associated with Payne — he determined that Payne's cell phone registered off of the Balmoral Towers cell tower on the night of the murder. The State then offered for admission Exhibit 10, a second map created by the Detective showing what he had determined to be the location of the Balmoral Towers cell tower, as well as the location of the crime scene.13

Based on Detective Edwards's testimony, the Assistant State's Attorney, in his closing, repeatedly urged that Payne's and Bond's Call Detail Records "point to their guilt" and the "evidence is significant ... because it puts them right there":

(italics added).

Clearly, Detective Edwards's testimony had significance in the present case. Whether the Detective should have been qualified as an expert before being allowed to engage in the process of identifying the geographic location of the cell towers and the locations themselves depends on understanding just what are cell phone records and what their contents reveal. Because understanding the significance of cell phone use in varying contexts extends far beyond merely placing and receiving phone calls, into e-mailing, photographing and internet browsing, (see Maeve Duggan & Lee Rainie, Pew Research, Cell Phone Activities 2012, 2 (Nov. 25, 2012), available at http://pewinternet.org/Reports/2012/ Cell-Activities.aspx (last visited Dec. 8, 2014) (finding that more than half of cell phone owners use their cell phone to take pictures, send or receive text messages, or access the internet)), the potential retrievable information from cell phone use is extensive.14 See Rick Ayers et al., Guidelines on Mobile Device Forensics 48-49 (May 2014), available at http://dx.doi.org/ 10.6028/NIST.SP.800-101r1 (last visited Dec. 8, 2014).

A cell phone is, effectively, a sophisticated two-way radio that operates within a cellular network. Clifford S. Fishman & Anne T. McKenna, Wiretapping & Eavesdropping: Surveillance in the Internet Age § 28:2 (3d ed. 2014). A cellular network is a wireless network added to the Plain Old Telephone System (POTS), which is the regular, wired form of telecommunications. Larry E. Daniel & Lars E. Daniel, Digital Forensics for Legal Professionals: Understanding Digital Evidence From the Warrant to the Courtroom § 33.1 (2012). In order to add a cellular network to the POTS network, equipment is added to the existing telecommunications system. Id. One piece of that equipment is the cell tower and its attached antennae, which is itself one component of a cell site.15 Id. It is through the cell tower that a cell phone maintains a connection to the telecommunications network. Id.

Cellular networks are comprised of a distribution of land areas called "cells", each of which is served by at least one cell tower. Id. The arrangement of cells "is based on the concept of dividing the landscape into coverage cells typically three miles in diameter", (Anna F. Tapp, Mapping the Impact of Vegetation and Terrain on Cellular Signal Levels 4 (2008), available at http://libres.uncg.edu/ir/uncg/f/umi-uncg-1612.pdf (last visited Dec. 8, 2014)); therefore, the term "cell" refers to a defined geographic region. Fishman & McKenna, supra, at § 28:2. These cells are "arranged in the pattern of a hexagonal grid or honeycomb." Aaron Blank, The Limitations and Admissibility of Using Historical Cellular Site Data to Track the Location of a Cellular Phone, 18 Rich. J. L. & Tech. 3, 5 (2011), citing In re Application of the United States for an Order for Prospective Cell Site Location Info. on Certain Cellular Tel., 460 F.Supp.2d 448, 450 (S.D.N.Y.2006). A cellular network is designed so that the cells overlap,16 (Tapp, supra, at 4), and the cell tower lies where the several cells intersect, not at the center of a cell.17 Fishman & McKenna, supra, at § 28:2. The coverage of a particular cell may range from one-half mile,18 particularly in the urban environment, to as far as thirty miles from the cell tower. Blank, supra, at 5.

There are a variety of factors affecting to which tower a cell phone will connect, beyond merely the distance between the originating cell phone, the receiving cell phone and the cell tower. These factors include technical characteristics of the site itself, such as the availability of a site and its location; technical characteristics of the antennae on a site, such as the direction they are facing; technical characteristics of the phone; and environmental and geographical factors:

Id. at 6-7. See also United States v. Evans, 892 F.Supp.2d 949, 956 (N.D.Ill.2012) (describing the factors that could cause a phone to connect to a particular site, including the locations of buildings and high volumes of network traffic); Tapp, supra, at 7, 9 ("A radio wave is impacted most by the physical nature of the land cover"; "Without line of sight or near line of sight access to an antenna, the cellular phone will not receive a signal, regardless of its distance to the transmitter.").19

All cell phones connect to a cell tower for, inter alia, communication.20 Daniel & Daniel, supra, at § 33.2.1. "Communication" occurs when a phone call is initiated, or a text message sent. See United Nations Global Pulse, Mobile Phone Network Data for Development at 1 (Oct. 2013), available at http://www.unglobalpulse.org/ sites/default/files/Mobile%20Data%20for%20Development%20Primer_Oct2013.pdf (last visited Dec. 8, 2014). Records of a communication via a cell phone may be classified as either external or internal; external records are those that exist outside of the cell phone, typically with the cell service provider, while internal records are those stored in the phone itself.21 See Timothy M. O'Shea & James Darnell, Admissibility of Forensic Cell Phone Evidence, 59 United States Attorneys' Bulletin 42, 42 (2011).

External records may be designated as to whether they are historical or prospective in nature. See United States v. Jones, 908 F.Supp.2d 203, 207 (D.D.C.2012). Historical and prospective data not only differ because of the temporal nature of the records, but the purpose of their creation.22 Historical data is that which has already been created and is already in existence as records kept in the course of the cell service provider's business for "billing, coverage, and analytics" purposes, (Daniel & Daniel, supra, at § 33.3), and include subscriber list information,23 text message details, Call Detail Records,24 bill copies and payment histories. See Law Enforcement Legal Compliance Guide, Verizon 8 (May 5, 2008), available at https://www.aclu.org/files/cellphonetracking/20120328/celltrackingpra_irvine7_irvineca.pdf (last visited Dec. 8, 2014) (hereinafter "Verizon legal compliance guide"); State v. Cotham, No. M2012-01150-CCA-R3-CD, slip op. at 11, 2014 WL 3778613 (Tenn.Crim.App. July 31, 2014) (testifying officer explained "that historical records were created by the phone company in the normal course of business"); Thomas A. O'Malley, Using Historical Cell Site Analysis Evidence in Criminal Trials, 59 United States Attorneys' Bulletin 16, 22-23 (2011) (discussing cellular service providers' "[r]ecordkeeping for business and maintenance").

"Whenever a mobile phone call or transaction is made, a Call Detail Record (CDR) is automatically generated by the mobile network operator."25 United Nations Global Pulse, supra, at 1. The information contained in a Call Detail Record is not entirely standardized, (id.), but there are certain fields regularly shown, including the location of the cell tower the phone connects to at the start of the call. Ayers, supra, at 73. Any change in the tower to which a cell phone connects during a call, however, is not necessarily included in the Call Detail Record.26 Id.

Cell tower location is typically presented in a Call Detail Record by way of a "cell tower identification number". Daniel & Daniel, supra, at § 33.4. As presented in a Call Detail Record, this information is coded in ways specific to the cellular provider, typically including a LAC ID and a Cell ID.27 Id. The specific location of a tower listed on the record then depends on determining, from those IDs, the cell tower which received the call, but not the location of that cell tower relative to the phone, nor, necessarily, any intervening cell towers which may have picked up the communication. Once the tower's cell tower identification number is identified, those numbers are matched with a list of cell towers provided by the cellular company, where an address or latitude and longitude for the tower in question may be determined. Id. at § 33.4.

Against the foregoing technical background, the question becomes whether Detective Edwards, when testifying about the process by which he derived the communication path of Payne's and Bond's cell phone calls, as well as his conclusion that the Menlo Drive cell tower and the Balmoral Towers cell tower were the most pertinent towers utilized by Payne's and Bond's cell phones,28 needed to be qualified as an expert.29 Answering this question also depends upon a review of Maryland Rules 5-70130 and 5702.31

A non-expert witness may offer opinion testimony in very limited circumstances, as proscribed by Maryland Rule 5-701, which allows a lay witness to offer an opinion that is both "(1) rationally based on the perception of the witness and (2) helpful to a clear understanding of the witness's testimony or the determination of a fact in issue." The rationale for the standard set by Rule 5-701 is two-fold: the evidence must be probative; in order to be probative, the evidence must be rationally based and premised on the personal knowledge of the witness. See Md. Rule 5-402.32

Expert testimony is governed by Maryland Rule 5-702. Rule 5-702 provides that expert testimony "may be admitted, in the form of an opinion or otherwise, if the court determines that the testimony will assist the trier of fact to understand the evidence or to determine a fact in issue." (italics added). Testimony elicited from an expert provides useful, relevant information when the trier of fact would not otherwise be able to reach a rational conclusion; such information "is not likely to be part of the background knowledge of the judge or jurors themselves." David H. Kaye, David E. Bernstien, & Jennifer L. Mnookin, The New Wigmore: Expert Evidence § 1.1 (2d ed. 2010). The trial judge, thus, determines whether to admit expert testimony dependent upon whether the witness could provide assistance to the finder of fact on the subject matter where a juror, lacking knowledge in a particular field, would resort to mere speculation and conjecture. See Rule 5-702.

In Ragland v. State, 385 Md. 706, 870 A.2d 609 (2005), we were confronted with a question, similar to that which we confront in the instant case, of whether police officers could render an opinion, based on their experience and without having to be qualified as experts under Rule 5-702, that certain conduct by the defendant constituted a drug transaction. In determining that the officers had to be qualified as experts, we adopted "the approach as reflected in the 2000 amendment to Fed. R.Evid. 701 and [held] that Md. Rules 5-701 and 5-702 prohibit the admission as `lay opinion' of testimony based upon specialized knowledge, skill, experience, training or education." Id. at 725, 870 A.2d at 620. We required the police officers in Ragland to be qualified as experts, because the opinions they formed regarding the nature of the defendant's actions as those of a drug transaction, were based on their "training and experience" derived from the "considerable time [they had devoted] to the study of the drug trade." Id. at 726, 870 A.2d at 620.

We applied Ragland in State v. Blackwell, 408 Md. 677, 697, 971 A.2d 296, 307 (2009), in order to limit the State from offering "an expert witness in lay witness clothing." In Blackwell, we explored whether an officer's testimony regarding the result of a horizontal gaze nystagmus (HGN) test he had performed on Blackwell during a traffic stop allegedly reflecting Blackwell's inebriation constituted expert testimony.33 The State had asserted that the officer's testimony was not subject to Rule 5-702, because the officer "did not expressly provide an opinion as to Blackwell's state of intoxication." Id. at 693, 971 A.2d at 305 (internal quotation marks omitted). We observed, however, that the HGN test differs from other field sobriety tests with which a person could "rely upon his or her personal experience", because "testimony [about HGN] has no significance to the average juror without an additional explanation of the scientific correlation between alcohol consumption and nystagmus". Id. at 692, 971 A.2d at 304. In so doing, we opined that Rule 5-702 encompasses testimony regarding "more than just `opinions.'" Id. at 693, 971 A.2d at 305.

In the present case the State asserts that Ragland and Blackwell are distinguishable from the present case because Detective Edwards did not render an opinion as to the location of Payne's and Bond's cell phones and that he merely read Sprint Nextel's business records and followed its directions in interpreting the data. We disagree. Detective Edwards engaged in a process to derive his conclusion that Payne's and Bond's cell phones communicated through the Menlo Park and Balmoral Towers cell towers that was beyond the ken of an average person; his conclusions regarding the communication path also required that he be qualified as an expert witness. Although the State urges that a "layperson with the same phone records and instructions could have determined the location of the cell sites" (even aside from the fact that the jury never received the full records and that the "step-by-step" instructions were developed from another source), additional training and experience were required to parlay the process from which Detective Edwards derived the communication path of each call.34

A Call Detail Record contains a string of data unfamiliar to a layperson and is not decipherable based on "personal experience". See Blackwell, 408 Md. at 692, 971 A.2d at 304. Detective Edwards, however, apparently relied on his experience to hone in on the entries in the Call Detail Records "pertinent" to the case. To understand, furthermore, the technical language of the entries in a Call Detail Record so that he could eliminate "extraneous" data in the records, Detective Edwards had to have relied on "knowledge, skill, experience, training or education." See Ragland, 385 Md. at 725, 870 A.2d at 620.

Once Detective Edwards had culled the records, he further relied on his knowledge and experience to understand the significance of a "LAC ID" and "Cell ID" and how they related to identifying a particular cell tower amongst a cellular provider's records. Detective Edwards's testimony was that of an expert, because Call Detail Record entries are not entries typical of a cell phone bill where a juror could "rely upon his or her personal experience" to understand their meaning. Blackwell, 408 Md. at 692, 971 A.2d at 304.

Detective Edwards needed to be qualified as an expert in order to also opine regarding the Menlo Drive and Balmoral Towers cell towers. Using the data he derived from his experience and expertise, Detective Edwards urged that he had determined the location of the cell towers through which Payne's and Bond's cell phone connected on the night of the murder and their location relative to the crime scene, which only an expert could derive, based upon the fact that a cell phone may connect to several towers during a call which may not be recorded.

We draw sustenance for our requirement of expert testimony in the instant case from United States v. Ganier, 468 F.3d 920, 925 (6th Cir.2006), in which the United States Court of Appeals explored whether a witness who testified regarding the results obtained by "running commercially-available software" to examine files on a computer was required to be qualified as an expert under Federal Rule of Evidence 702. The Government had urged that the witness's testimony was not based on "scientific, technical, or other specialized knowledge", because he was merely reading the results provided by running the software, and the testimony was of the same types of facts "that could be observed by any person reasonably proficient in the use of commonly used computer software". Id. at 925-26. The Sixth Circuit rejected the Government's argument and held that reading the results produced by running the program required expertise, explaining that a "layperson today may be able to interpret the outputs of popular software programs", but the "reports generated by the forensic software display a heading, a string of words and symbols, date and time, and a list of words" which would have been unfamiliar to a lay witness without specialized knowledge and experience. Id. at 926.

As a result of our determination that Detective Edwards was obligated to have been qualified as an expert, a retrial will be required, as the Court of Special Appeals concluded as well. Should the State choose to pursue the case against Payne and the trial judge does not sever Payne's case from Bond's, the issue may again arise regarding the admissibility of six wiretapped telephone conversations captured on the Baltimore County police wiretap, in which Payne was not recorded as a participant. Payne has raised the issue of the admissibility of the calls in his cross-petition in which he asks, "Did the Court of Special Appeals err in ruling that wiretap statements made by respondent Bond but not respondent Payne were nevertheless admissible against Payne as statements by a party-opponent?"

The facts pertinent to the wiretapped statements were that Tyrice McCant and Brittany Keller were individually confronted by police two months after Glen Stewart's murder in October and early November 2007, respectively; both told police that Payne, Bond and others were with Keller the night of the incident assisting her with car trouble, thereby providing Payne and Bond with an alibi. At trial, both women recanted their stories. Keller also testified that she discussed the need to maintain the false alibi with Bond in December 2007 in one cell phone conversation, a taped version of which was played at trial and admitted into evidence against Payne as a statement of a co-conspirator. Keller also testified about a face-to-face meeting with Payne in December 2007; in her testimony, she said: "As far as Joey was concerned, I spoke with him about what was said by Jason, but I didn't know what he was going to do as far as the police were concerned."35

Desmond Jones, an indicted co-conspirator who had pled guilty prior to trial, also testified at trial, during which five calls between Bond and Jones were played for the jury and also admitted into evidence against Payne as statements of co-conspirators. With respect to the six recorded telephone conversations, the State, in its brief, identified them as occurring within three hours of one another on December 12, 2007, after detectives had questioned Bond regarding the night of the crime, and described the calls as follows:

(Extract and transcript references omitted).

At trial, the State argued in support of the introduction of the six telephone calls against Payne and Bond that the conversations were statements of co-conspirators under Rule 5-803(a)(5).37 The State asserted that the conspiracy forming the foundation for the introduction of these statements was a conspiracy to conceal the murder of Stewart, to which Keller and Bond had provided an alibi. The State argued to the trial court that Keller's face-to-face conversation with Payne on December 12, 2007, proved Payne's participation in the conspiracy to conceal. Months prior to trial, the State had proffered that DNR Reports reflecting a number of telephone calls between Payne, McCant, Keller, Bond, Johnson and Jones also linked the individuals together in a conspiracy to conceal.

Payne argued before the trial court that he was not a part of any conspiracy to conceal, that he was not a participant in any of the six calls and that the statements made during the calls were inadmissible hearsay. According to Payne, the State just did not prove that he was a part of any conspiracy.

Before the phone call between Bond and Keller was played at trial, the trial judge specifically questioned how it was admissible against Payne and ultimately decided that "all the players knew that" a false alibi had been offered to police, which was "the genesis of conspiracy." In so ruling, the judge referred to Keller's testimony regarding her face-to-face meeting with Payne as sufficient to provide the foundation for a conspiracy to allow the six statements to come in as to Payne:

During Jones's testimony, the trial judge indicated, based upon her prior ruling as to the admissibility of the Bond and Keller call, that she thought there was an adequate foundation to admit the five calls between Bond and Jones against Payne and Bond.

Before the Court of Special Appeals, the State again relied on Keller's testimony about her face-to-face meeting with Payne as sufficient proof of a conspiracy to conceal; the State also argued that "efforts to burn the victim's body" was additional proof of a conspiracy to conceal.

The Court of Special Appeals disagreed with the trial court and denied the admissibility of the statements against Payne or Bond as statements of co-conspirators under Rule 5-803(a)(5), because there was no evidence of a conspiracy to conceal:

Payne & Bond, 211 Md.App. at 250, 65 A.3d at 171-72. The Court of Special Appeals seemingly stated, however, that the telephone calls were admissible as statements of party opponents under Rule 5-803(a)(1)38 as to Payne, although the State before us questioned that the paragraph in the Court of Special Appeals opinion so held; the paragraph stated:

Payne & Bond, 211 Md.App. at 252, 65 A.3d at 172-73. Later in the opinion, however, our intermediate appellate court stated, "Accordingly, we are persuaded that the wiretap recordings were admissible as to both Payne and Bond as statements of a party opponent. The trial court properly exercised its discretion in admitting them, albeit on grounds different than argued by the parties at trial." Id. at 253-54, 65 A.3d at 173.

The State, nevertheless, urges before us that, "[t]he Court of Special Appeals did not hold that Bond's statements were admissible against Payne; it held that Bond's statements were admissible against him as statements of a party-opponent." The State also argues that Bruton v. United States, 391 U.S. 123, 88 S.Ct. 1620, 20 L.Ed.2d 476 (1968) is not violated because the telephone conversations did not implicate "Payne as an accomplice to the kidnapping and murder of Stewart". Finally, the State argues that the introduction of the recordings of the six telephone calls against Payne was harmless error, because "there was a plethora of other evidence...."

Before us, Payne disputes that the party opponent rule, Rule 5-803(a)(1), applies and permits the admission of the six telephone calls because Bond was not his party opponent; he unequivocally questions the evidentiary foundation for the admission of the six recordings at all. The error in the admission of the recordings is not harmless, he states, because there is no evidence that he was a part of any conspiracy to conceal.

The party opponent rule, Rule 5-803(a)(1), provides that, "A statement that is offered against a party and is ... [t]he party's own statement, in either an individual or representative capacity" is "not excluded by the hearsay rule". We have a dearth of authority in Maryland interpreting who a party opponent is, so we turn to our federal counterparts for assistance.

Federal Rule 801(d)(2)(A),39 adopted in 1975, is on all fours with our Rule 5803(a)(1). In interpreting who is a party opponent in the context of a criminal case in which there are multiple defendants, the Second and Eleventh Circuit Courts of Appeals have decried that a co-defendant cannot be a party opponent; only the Government is. In United States v. Harwood, 998 F.2d 91, 94 (2d Cir.1993), Harwood and McKee were jointly tried. McKee had made statements to a journalist about Harwood's involvement, which Harwood tried to introduce at trial as exculpatory, and on appeal, argued that the statements were admissions by a party opponent under Federal Rule of Evidence 801(d)(2)(A). The trial court rejected the evidence, and the Second Circuit affirmed, "because the admission sought to be introduced was made by a co-defendant who is not a party opponent. The Government is the party opponent of both defendants." Id. at 97-98, quoting United States v. Gossett, 877 F.2d 901, 906 (11th Cir.1989) (per curiam), cert. denied, 493 U.S. 1082, 110 S.Ct. 1141, 107 L.Ed.2d 1045 (1990). In the instant case, Payne and Bond were tried together, and the State is the opponent of both; neither of them was the party-opponent of the other.

Whether the six telephone calls can be properly admitted against Payne as statements of a co-conspirator under Rule 5-803(a)(5) with regard to a conspiracy to conceal depends upon the State having advanced a prima facie case that a conspiracy to conceal existed and, secondly, Payne's agreement to the conspiracy. Rule 5-803(a)(5) states that "a statement by a coconspirator ... during the course and in furtherance of the conspiracy ..." is "not excluded by the hearsay rule". The Court of Special Appeals determined that no conspiracy to conceal existed, so that Rule 5-803(a)(5) was not implicated as to Payne and Bond, opining that there was an absence of proof of "an express agreement between the parties, at the outset, to engage in concerted acts of concealment after committing the kidnapping and murder", (Payne & Bond, 211 Md.App. at 250, 65 A.3d at 171), and further stated:

Id. at 250, 65 A.3d at 171-72. In so doing, our intermediate appellate court relied on the strictures of State v. Rivenbark, 311 Md. 147, 158, 533 A.2d 271, 276 (1987), which held that the "statements made in connection with acts of concealment performed long after the conspirators have realized all benefits from the offense which they had agreed to commit" are inadmissible.

Although we agree with our intermediate appellate court that Rivenbark is controlling regarding the conspiracy to conceal, we disagree that there was not a prima facie showing of a conspiracy to conceal that could have gone to the jury,40 (see Hill v. State, 231 Md. 458, 190 A.2d 795 (1963)), though proof of Payne's participation was lacking.

In Rivenbark, 311 Md. at 150, 533 A.2d at 272, Ronald Johnson and Billy Rivenbark robbed and murdered Johnson's aunt. That same day, after the murder, Rivenbark told Shirley Wilson, Johnson's girlfriend, that "[w]e got our alibis.... As long as everyone stays cool everything will be fine." Id. at 151, 533 A.2d at 272. Rivenbark later told Wilson that he and Johnson "should not see each other for a while", and Johnson inflicted numerous beatings on Wilson in order to ensure her silence. Id. at 151, 533 A.2d at 272-73.

In Rivenbark, we expressly considered "whether every criminal conspiracy includes, by implication, a subsidiary conspiracy to conceal evidence of the substantive offense that the conspirators agreed to commit." Id. at 152-52, 533 A.2d at 273. We recognized two separate instances where a conspiracy to conceal may arise; at the outset of the underlying criminal act or after the completion of the act as a second conspiracy. In responding to the issue, we rejected "the theory that every criminal conspiracy includes, by implication, a subsidiary conspiracy to conceal evidence of the substantive offense that the conspirators agreed to commit." Id. at 158, 533 A.2d at 276. We recognized, however, that "if the conspirators expressly agree at the outset to engage in concerted acts of concealment after committing a substantive offense, then statements made in connection with those acts are admissible." Id. Regarding a subsequent conspiracy, we explained in Rivenbark that the evidence did not show an ongoing distinct and explicit agreement to conceal the underlying offense:

Id. at 159, 533 A.2d at 277.

Agreement is the essence of a conspiracy, as we opined in State v. Johnson, 367 Md. 418, 424, 788 A.2d 628, 632 (2002), in which we further stated that, "This Court consistently has defined conspiracy as the agreement between two or more people to achieve some unlawful purpose or to employ unlawful means in achieving a lawful purpose." We have summarized the elements of a criminal conspiracy to be:

Townes v. State, 314 Md. 71, 75, 548 A.2d 832, 834 (1988). See Mason v. State, 302 Md. 434, 444, 488 A.2d 955, 960 (1985) (stating that the "agreement is the crime, and the crime is complete without any overt act"); Monoker v. State, 321 Md. 214, 221, 582 A.2d 525, 528 (1990) ("The gist of conspiracy is the unlawful agreement.... The crime is complete when the unlawful agreement is made").

As to Payne, the State did not prove that he agreed to participate in a conspiracy to conceal, either from the beginning or subsequent to the murder. Although the trial court relied exclusively on Keller's testimony about her face-to-face meeting with Payne to establish that he agreed with the conspiracy to conceal, in which she said, "As far as Joey was concerned, I spoke with him about what was said by Jason, but I didn't know what he was going to do as far as police were concerned", Keller related no response from Payne reflecting that he had agreed to participate in an agreement to conceal.

In an attempt to augment what the trial court relied upon to determine that Payne was part of a conspiracy to conceal, the State before us refers to the DNR reports showing telephone calls, without corresponding content, that occurred between Payne, Keller, McCant, Bond, Jones and Johnson during the time that McCant and Keller were interrogated by police. In addition to the fact that the trial court did not rely on these to admit the calls, the DNRs do not provide additional proof that Payne expressly agreed to a conspiracy to conceal. The DNRs only provide a list of phone numbers dialed from specific phones, without any proof of who dialed the numbers, let alone any content from the calls.

The State's final allegation is that Jones's testimony about the burning of the victim's body shows that Payne conspired to conceal, although this also was not relied upon by the trial court in the admission of the statements. Jones's testimony, however, does not reflect that Payne was a party in a conspiracy to conceal.41

Should the State pursue a joint trial of Payne and Bond and wish to introduce as evidence the six wiretapped recordings against Bond, there are further inquiries that the Circuit Court must make.

The State asserts that the six recordings were non-testimonial and, therefore, could be played during a joint trial of Payne and Bond and introduced into evidence only against Bond, without violating the tenets of Bruton v. United States, 391 U.S. 123, 88 S.Ct. 1620, 20 L.Ed.2d 476 (1968). Payne disagrees, asserting that, under Bruton, his trial should be severed from Bond, because he cannot adequately defend himself under the Confrontation Clause should the recordings be played. We agree, however, with the State as to the Bruton issue, because the six wiretapped conversations are non-testimonial in character under Crawford v. Washington, 541 U.S. 36, 124 S.Ct. 1354, 158 L.Ed.2d 177 (2004), and so do not implicate Payne's Confrontation Clause rights.

Crawford defines the analysis for determining whether the admission of a hearsay statement violates an accused's right of confrontation under the Sixth Amendment.42 Crawford, 541 U.S. at 68, 124 S.Ct. at 1374, 158 L.Ed.2d at 203. See Cox v. State, 421 Md. 630, 642, 28 A.3d 687, 694 (2011) (noting that "we analyze the admission of out-of-court statements against criminal defendants under the framework created by the United States Supreme Court in Crawford v. Washington"). The Confrontation Clause analysis is triggered when hearsay, sought to be introduced, is "testimonial" in nature. Crawford, 541 U.S. at 68, 124 S.Ct. at 1374, 158 L.Ed.2d at 203. See Cooper v. State, 434 Md. 209, 233, 73 A.3d 1108, 1122 (2013) ("[T]he right of confrontation is implicated only when two conditions are met: the challenged out-of-court statement or evidence must be presented for its truth and the challenged out-of-court statement or evidence must be `testimonial.'").

While the Crawford Court did not provide a comprehensive definition of the word "testimonial", it did provide several specific examples of such evidence. Crawford, 541 U.S. at 68, 124 S.Ct. at 1374, 158 L.Ed.2d at 181 (listing "prior testimony at a preliminary hearing, before a grand jury, or at a former trial" and "police interrogations"). We have held that the proper inquiry to determine whether a statement is testimonial is "whether a reasonable person in the declarant's situation would have made the statement `with a primary purpose of creating an out-of-court substitute for trial testimony.'" Cox, 421 Md. at 650, 28 A.3d at 698, quoting Michigan v. Bryant, 562 U.S. 344, ___, 131 S.Ct. 1143, 1155, 179 L.Ed.2d 93, 107 (2011).

In Cox, we considered whether statements implicating Cox, made by a co-conspirator to a jailhouse acquaintance cooperating with the authorities, were testimonial and could be introduced against Cox through the testimony of the jailhouse cooperator. When we considered whether the inmate's testimony violated Cox's Confrontation Clause rights, we held that the "spontaneous" statements implicating Cox made by the coconspirator during the jailhouse discussion were non-testimonial, because "the interaction was casual conversation between private acquaintances" and the statements "were not made for the primary purpose of creating a substitute for trial testimony." Id. at 650-51, 28 A.3d at 699. As a result, we affirmed Cox's conviction.

As in Cox, the six wiretapped recordings in the present case were "more akin to casual remarks to an acquaintance than formal declarations to an official", id. at 650, 28 A.3d at 699, and, thus, were non-testimonial under Crawford. Various of our brethren in the federal system, when faced with wiretap evidence, have also recognized that the conversations are not testimonial. United States v. Ramirez, 479 F.3d 1229, 1249 (10th Cir.2007) (holding statements of co-conspirators procured through a wiretap are non-testimonial); United States v. Hendricks, 395 F.3d 173, 181 (3d Cir.2005) (holding that surreptitiously monitored private conversations and statements contained in wiretap recordings are not testimonial for purposes of Crawford, because, inter alia, "the speakers certainly did not make the statements thinking that they `would be available for use at a later trial'", quoting Crawford, 541 U.S. at 52, 124 S.Ct. at 1364, 158 L.Ed.2d at 193).

Because Crawford is not implicated by the six recordings, Payne's Bruton rights are not triggered. Bruton rights are triggered when testimonial hearsay is introduced into evidence. In Bruton, the Supreme Court addressed "whether the conviction of a defendant at a joint trial should be set aside although the jury was instructed that a codefendant's confession inculpating the defendant had to be disregarded in determining his guilt or innocence." Bruton, 391 U.S. at 124-25, 88 S.Ct. at 1622, 20 L.Ed.2d at 478. During Bruton's joint trial with Evans, Evans's out of court confession inculpating both defendants had been admitted into evidence. The trial judge had given a limiting instruction to the jury to consider the confession only against Evans, but not against Bruton. The United States Court of Appeals for the Eighth Circuit affirmed. Bruton v. United States, 375 F.2d 355 (8th Cir.1967).

The Supreme Court reversed. The Court held that the trial court's limiting instruction did not sufficiently protect Bruton's Sixth Amendment rights, because Evans had not testified, the introduction of Evans's confession added substantial weight to the Government's case against Bruton, and Bruton could not cross-examine Evans. Bruton, 391 U.S. at 137, 88 S.Ct. at 1628, 20 L.Ed.2d at 485. The Court opined that a limiting instruction was insufficient to protect Bruton's right to cross-examine and that there was no basis upon which to admit Evans's confession against Bruton. When "the powerfully incriminating extrajudicial statements of a codefendant, who stands accused side-by-side with the defendant, are deliberately spread before the jury in a joint trial", the Court concluded, "limiting instructions [were not acceptable] as an adequate substitute for [Bruton's] constitutional right of cross examination." Id. at 135-36, 137, 88 S.Ct. at 1628, 20 L.Ed.2d at 483, 484. Bruton, then, is premised upon the Confrontation Clause of the Sixth Amendment and limits joinder, as well as the efficacy of cautionary instructions when evidence of a testimonial nature is introduced. See United States v. Avila Vargas, 570 F.3d 1004, 1008-09 (8th Cir.2009) (holding that Bruton does not apply to non-testimonial co-conspirator statements); United States v. Johnson, 581 F.3d 320, 326 (6th Cir. 2009) (opining that "Because it is premised on the Confrontation Clause, the Bruton rule, like the Confrontation Clause itself, does not apply to nontestimonial statements"); United States v. Smalls, 605 F.3d 765, 768 n. 2 (10th Cir.2010) (noting that "the Bruton rule, like the Confrontation Clause upon which it is premised, does not apply to nontestimonial hearsay statements"); United States v. Figueroa-Cartagena, 612 F.3d 69, 85 (1st Cir.2010) (noting that it is "necessary to view Bruton through the lens of Crawford").

As a result, because the six wiretapped recordings in this case are non-testimonial, their admission in a joint trial does not implicate Payne's Confrontation Clause rights under Crawford and Bruton.

The trial court, nevertheless, must consider whether joinder or a cautionary instruction will sufficiently avoid prejudice to Payne under the tenets of Maryland Rule 4253(c):

Because we have stated that Payne was not a party to a conspiracy to conceal and not a party-opponent of Bond, the six telephone recordings are not admissible against Payne under a hearsay exception. We acknowledged in Galloway v. State that "[p]rejudice within the meaning of Rule 4-253 is a `term of art' and refers only to prejudice resulting to the defendant from the reception of evidence that would have been inadmissible against that defendant had there been no joinder." 371 Md. 379, 394 n. 11, 809 A.2d 653, 663 n. 11 (2002), quoting Ogonowski v. State, 87 Md.App. 173, 186-87, 589 A.2d 513, 520 (1991). Therefore, the implication of Rule 4-253(c) also must be considered on remand in this case, insofar as Payne is concerned.

In conclusion, based on our review of the intricacies of "cell phone records" and the training, experience and expertise required by Detective Edwards to determine the alleged cell towers with which Payne's and Bond's cell phones communicated, we conclude that Detective Edwards should have been qualified as an expert witness under Maryland Rule 5-702, and remand the cases for a new trial. As guidance in the new trial, we also conclude that Bond's statements in the six recordings obtained off of wiretaps could not be admitted against Payne as the statement of a party opponent and that, while there may have been sufficient evidence to establish a prima facie showing of a conspiracy to conceal, the evidence did not support the determination that Payne was a part of that conspiracy.

JUDGMENT OF THE COURT OF SPECIAL APPEALS VACATED. CASE REMANDED TO THE COURT OF SPECIAL APPEALS WITH INSTRUCTIONS TO VACATE THE JUDGMENT OF THE CIRCUIT COURT FOR BALTIMORE COUNTY AND REMAND THE CASE TO THE CIRCUIT COURT FOR A NEW TRIAL CONSISTENT WITH THIS OPINION. COSTS IN THIS COURT AND THE COURT OF SPECIAL APPEALS TO BE PAID BY THE PETITIONER.

BARBERA, C.J., HARRELL and McDONALD, JJ., concur.

McDONALD, J., concurring, which BARBERA, C.J., and HARRELL, J., join.

I concur in the Court's judgment, but not in its opinion. When a judge on this Court concurs in the judgment only, it is helpful to explain why. Then the reader knows whether there is a substantive reason for that judge's reticence and can assess whether that reason has any merit. So — here goes.

The Majority holds that Detective Brian Edwards should have been qualified by the trial court as an expert under Maryland Rule 5-702 to testify as to the process for determining the communication path of the defendants' cell phones and as to the importance of two particular cell towers. Majority op. at 684-85, 104 A.3d at 144. This holding appears based on a conclusion that Detective Edwards gave expert opinion testimony at trial. In my view, he did not.

At the trial, Detective Edwards essentially applied the telephone company's key to the cell phone records of the defendants and determined that their cell phones had registered off certain cell phone towers in the vicinity of the crime during its commission and cover-up. As the trial judge stated, the process that Detective Edwards used to locate the cell towers associated with particular calls on the telephone company records "isn't rocket science." An analogy closer to home may illustrate the point. A particular court may denominate a case with a designation like "Civ. No. S-14-0026." One who has the key knows that this means that the particular action is a civil case ("Civ.No.") assigned to Judge Smith ("S") and was the 26th such case ("0026") filed in the court in 2014 ("14"). One need not be a legal expert (i.e., a lawyer) to decipher the case designation, although perhaps a lawyer would be necessary to explain accurately the claims and defenses in the action.

Thus, in my view, Detective Edwards did not provide expert testimony and need not have been qualified as an expert to provide that testimony.

Why, then, do I concur in the judgment? In my view, there was a gap in the prosecution's proof that undermined the probative value of Detective Edwards' testimony. Information concerning the location of the cell phone towers associated with particular calls was only probative if it was evidence of where the defendants — or at least their phones — were located at the time of those calls. At the end of the trial the prosecutor argued that the fact that calls on the defendants' cell phones registered off cell phone towers in close proximity to the crime scenes was corroboration for the testimony that the defendants had been present and participated in those crimes.

But there was no testimony at trial as to the significance of the location of a cell phone tower in relation to the location of the user of the phone. In some communication technologies, the path taken by a message over the communications infrastructure may vary and the intermediate route may reveal little about the location of the sender or receiver. For example, each time one obtains a copy of this opinion over the Internet, the transmission may take a very different route to the same destination.1

Based on the technical discussion in the Majority opinion on cell phone technology2 and some readily available technical sources,3 it appears that the inference urged by the prosecutor was likely correct. But we do not want jurors checking readily available technical resources — or even judicial opinions — to obtain technical information concerning the significance of the evidence before them. A properly qualified expert — perhaps an electrical engineer or a communications engineer — was needed. It would likely not have been the most sophisticated testimony concerning wireless communications, but it is not something that can be said to be within the common knowledge of a lay juror. Without such testimony, the jury was left to speculate — perhaps reaching a correct conclusion, but still speculating — as to the significance of the cell towers' location.

In the absence of expert testimony that would allow the jury to understand the significance of the towers' location, the testimony concerning the location of the cell towers was not admissible under Maryland Rules 5-402 (only relevant evidence admissible) and 5403 (even relevant evidence may be excluded if relevance is outweighed by confusion).

Chief Judge BARBERA and Judge HARRELL have advised that they join this opinion.

APPENDIX A

APPENDIX B

APPENDIX C

Tom Farley & Mark van der Hoek, Cellular Telephone Basics, Private Line (Jan. 1, 2006, 8:55 PM), http://www.privateline.com/mt_cellbasics/.