OPINION BY BENDER, P.J.E.:

Ollie Thompson appeals from the judgment of sentence of 5-10 years' incarceration imposed following his conviction for possession with intent to deliver a controlled substance (PWID), 35 P.S. § 780-113(a)(30).1 We vacate the judgment of sentence and dismiss the charges against Appellant pursuant to Pa.R.Crim.P. 600.

In December 2009, Appellant was arrested and charged with PWID and related offenses after police observed Appellant engage in an illegal narcotics transaction. In October 2011, the trial court denied Appellant's motion to dismiss filed pursuant to Rule 600, and this matter proceeded to a jury trial resulting in Appellant's conviction. In January 2012, the trial court sentenced Appellant to a mandatory sentence of 5-10 years' incarceration. See Commonwealth v. Thompson, 93 A.3d 478, 482-84 (Pa.Super.2014) (setting forth a more thorough recitation of the underlying facts and procedural history of this case).

Appellant timely appealed. Appellant challenged inter alia the trial court's Rule 600 analysis. Specifically, the trial court had recognized that two, significant periods of delay occurred when Appellant was not transported from state custody, resulting in an aggregate delay of approximately 309 days. The first period was from December 20, 2010, until May 9, 2011 (140 days); the second from May 9, 2011, until October 25, 2011 (169 days). Id. at 489. According to Appellant, these delays, which the trial court deemed "administrative error" and thus excusable, should have been attributed to the Commonwealth. Id. at 488. Upon review, a unanimous panel of this Court concluded that there was no evidence of record to support the trial court's cursory analysis. Id. at 488-89. We further determined sua sponte that Appellant's mandatory sentence was illegal. Id. at 493-94 (citing Alleyne v. United States, ___ U.S. ___, 133 S.Ct. 2151, 186 L.Ed.2d 314 (2013)). Accordingly, we vacated the judgment of sentence and remanded for further proceedings. Id. at 494.

Regarding Appellant's Rule 600 challenge, we directed the trial court to consider further the circumstances leading to the two delays:

Id. at 488-89 (footnote omitted).

On remand in August 2014, the trial court held an evidentiary hearing. The Commonwealth noted for the record that the Clerk of Quarter Sessions2 court docket revealed that Appellant had requested a continuance on December 20, 2010. See Notes of Testimony (N.T.), 08/22/2014, at 9-10. However, there was no similar notation regarding May 9, 2011. Id. To counter this lack of evidence, the Commonwealth introduced testimony from Attorney Alisa Shver who was the assistant district attorney assigned to the case at the time. A.D.A. Shver testified that her file did not indicate whether a writ was requested or prepared for May 9, 2011. N.T. at 20-21. Thereafter, the following exchange took place:

Id. at 21.

Appellant was not present at the hearing, and so the trial court withheld a decision pending arrangements for Appellant's transportation. Id. at 26. Thereafter, in October 2014, a second hearing occurred, at which time the trial court denied Appellant's Rule 600 challenge, finding the testimony of A.D.A. Shver credible and concluding that the Commonwealth had demonstrated by a preponderance of evidence that it had exercised due diligence in securing Appellant's presence for trial. N.T., 10/14/2014, 5-6. The trial court then resentenced Appellant as set forth above.

Appellant timely appealed and now raises the following issues:

Appellant's Brief at 4.3 In light of the following analysis, we do not reach Appellant's second question.

Appellant contends that the trial court erred as a matter of law, and thus abused its discretion, when it denied his Rule 600 motion to dismiss. "Rule 600 was designed to prevent unnecessary prosecutorial delay in bringing a defendant to trial." Commonwealth v. Brock, 619 Pa. 278, 61 A.3d 1015, 1021 (2013).

Commonwealth v. Selenski, 606 Pa. 51, 994 A.2d 1083, 1088 (2010) (internal punctuation and citations omitted).4

We review a trial court's decision to deny a Rule 600 motion for an abuse of discretion. Commonwealth v. Ramos, 936 A.2d 1097, 1100 (Pa.Super.2007).

Id.

In relevant part, Rule 600 requires that trial shall commence within 365 days from the date on which the complaint is filed. See Pa.R.Crim.P. 600(A). This straightforward calculation is known as the mechanical run date. See, e.g., Ramos, 936 A.2d at 1102. However, those periods of delay caused by a defendant are excluded from the computation of the length of time of any pretrial incarceration. Pa. R.Crim.P. 600(C). Following these exclusions, if any, we arrive at an adjusted run date by extending the mechanical run date to account for these exclusions. See, e.g., Ramos, 936 A.2d at 1102. Any other delay that occurs, despite the Commonwealth's due diligence, is deemed excusable and results in further adjustments to the effective run date. Pa.R.Crim.P. 600(G); see also Ramos, 936 A.2d at 1102 (explaining that "[e]xcusable delay is a legal construct that takes into account delays which occur as a result of circumstances beyond the Commonwealth's control and despite its due diligence") (internal punctuation and citation omitted).

To establish that a delay is excusable, the Commonwealth must demonstrate that it proceeded with due diligence by a preponderance of the evidence. Selenski, 994 A.2d at 1089; see also Commonwealth v. Hill, 558 Pa. 238, 736 A.2d 578, 586 (1999).

Selenski, 994 A.2d at 1089 (internal citations omitted). "Due diligence includes, among other things, listing a case for trial prior to the run date, preparedness for trial within the run date, and keeping adequate records to ensure compliance with Rule 600." Ramos, 936 at 1102 (emphasis added).

"[T]he Commonwealth should be held to the requirement that it exercise due diligence at all times during the pendency of a case." Commonwealth v. Hawk, 528 Pa. 329, 597 A.2d 1141, 1145 (1991). Thus, the Commonwealth must act with due diligence "throughout the period," for each delay not caused by the defendant. Hill, 736 A.2d at 586. This requires affirmative action by the Commonwealth. See Hawk, 597 A.2d at 1145 (rejecting the Commonwealth's argument that an assigned judge's unavailability precluded the Commonwealth from listing a case for trial).

Here, Appellant's trial commenced on October 25, 2011. This was well beyond the mechanical run date: The complaint was filed against Appellant on December 4, 2009, and thus, the mechanical run date was December 6, 2010. See Phila. Cnty. Crim. Complaint DC# 09-15-132041; Pa. R.Crim.P. 600(A)(2)(a); see also 1 Pa.C.S. § 1908.

Appellant was responsible for several periods of delay, totaling 150 days of excludable time. See N.T. (Rule 600 Motion Hearing), 10/24/2011, at 7-9.5 Thus, the apparent, adjusted run date was May 5, 2011.

Turning to the two remaining delays, which were the subject of the hearing on remand, evidence established that the first of these occurred when Appellant requested a continuance. See N.T., 08/22/2014, at 9-10. Accordingly, Appellant was also responsible for the period of delay from December 20, 2010, until May 9, 2011, totaling another 140 days of excludable time. Thus, the adjusted run date was actually September 22, 2011.

However, there was no evidence presented to the trial court that would justify excluding or excusing the final period of delay from the run date calculation. The delay was not attributable to Appellant. Further, the Commonwealth acknowledged that no writ issued to transport Appellant to trial on May 9, 2011, and there was no indication in the Quarter Sessions file or the district attorney's file that a writ was ever requested. Id.; see also N.T., 08/22/2014, at 20-21.

The Commonwealth sought to excuse this delay by relying on the testimony of A.D.A. Shver, who suggested that it was her standard procedure to request a writ. Id. at 21. Thus, the question arises whether her testimony demonstrates due diligence by the Commonwealth. If so, we may excuse the delay from May 9, 2011, until October 25, 2011.

According to Appellant, such testimony is insufficient. This is because, Appellant submits, "mere assertions of due diligence, as well as unsupported facts, are insufficient to meet the required burden." Appellant's Brief at 18 (quoting Commonwealth v. Caden, 337 Pa.Super. 390, 487 A.2d 1, 4 (1984)). In response, the Commonwealth maintains that Appellant's absence on May 9, 2011, should not be attributed to the Commonwealth. According to the Commonwealth, its habitual "use of the writ system constitutes due diligence, notwithstanding repeated failures of corrections officials to comply with the court's order to bring a defendant down from custody." Commonwealth's Brief at 15 (principally citing in support Commonwealth v. Mines, 797 A.2d 963 (Pa.Super.2002); see also Commonwealth's Brief at 16-18 (citing Pa.R.E. 406, which provides for the admissibility of evidence tending to prove an organization's routine practice occurred on a specific occasion)).

Appellant's argument is persuasive. Due diligence does not require perfect vigilance, but the Commonwealth must demonstrate affirmatively that it endeavored to secure a defendant's presence when necessary, throughout the pendency of the case. See Selenski, 994 A.2d at 1089; Hill, 736 A.2d at 586; Hawk, 597 A.2d at 1145.

Upon remand, we specifically directed the Commonwealth to demonstrate that it "sought a writ from the trial court to secure Appellant's presence in court" on May 9, 2011. Thompson, 93 A.3d at 489. It was unable to do so. In particular, the lack of any notation in the district attorney's file is troubling. See N.T., 08/22/2014, at 20-21. This failure to keep adequate records of its efforts to secure Appellant's presence at trial militates against any conclusion the Commonwealth acted with due diligence. See Ramos, 936 A.2d at 1102.

In our view, the Commonwealth's reliance upon Mines is misplaced, as it offers no justification for the Commonwealth's failure to document its efforts. In that case, we examined two delays caused when the defendant was not brought to trial. Mines, 797 A.2d at 964-65. Regarding one of the delays, the Quarter Sessions file failed to indicate whether a writ issued. Id. Nevertheless, we did not charge the delay to the Commonwealth. Id.

There are clear distinctions between Mines and the case sub judice. In Mines, there was no testimony or documentary evidence regarding the contents of the district attorney's file, and the focus of our analysis remained on the Quarter Sessions file. Id. Importantly, the question of whether the Commonwealth actually requested a writ never arose in Mines. Rather, we merely reasoned that any number of clerical errors could have led to the delay. Id. at 965 (concluding that "[t]here are many more possibilities that make it impossible for the [a]ssistant [d]istrict [a]ttorney to know whether a writ he or she requested was in fact prepared").6 Here, we sought to eliminate the potential confusion caused by clerical error or other, "plausible" reasons for the delay. See Thompson, 93 A.3d at 488-89. For these reasons, we deem Mines inapposite.

Moreover, A.D.A. Shver's credible testimony did not further inform the court. Despite the admissibility of evidence tending to establish the Commonwealth's habitual use of the writ system, see Pa.R.E. 406, such evidence does not pass the threshold requirements established in Hawk and Caden; i.e., mere assertions of due diligence are insufficient, rather due diligence requires affirmative action. Thus, regardless of whether it is the common practice or standard procedure for the Commonwealth to request a writ for a defendant's transportation, and we presume that it is, the issue here was whether the Commonwealth did so on a specific date. To be clear, we do not question the trial court's credibility determination. See N.T., 10/14/2014, 5-6. Rather, we hold that the credible testimony of A.D.A. Shver was insufficient to establish the Commonwealth's due diligence on May 9, 2011. See Hawk, 597 A.2d at 1145; Caden, 487 A.2d at 4.

In conclusion, we remanded this matter and directed the Commonwealth to establish that it sought Appellant's presence at trial with due diligence. Thompson. It was unable to do so with either documentary or testimonial evidence. Ramos; Caden. Accordingly, the trial court erred as a matter of law, and we deem this error to be an abuse of discretion. Ramos. Despite its assertion to the contrary, the Commonwealth failed to demonstrate that it took affirmative action to secure Appellant's presence for trial. Hawk; Caden. Accordingly, we may not excuse the delay in Appellant's trial from May 9, 2011, until October 25, 2011. Selenski; Pa.R.Crim.P. 600. For these reasons, the judgment of sentence is vacated; the charges against Appellant are dismissed; and Appellant shall be discharged.

Judgment of sentence vacated. Charges dismissed with prejudice. Appellant discharged.