BLACKWELL, Justice.

Billy D. Nicely was tried by a Hall County jury and convicted of the murder of Tayore Wright, a one-year-old girl. On appeal, Nicely contends that his father was denied equal protection when the father was excluded from portions of the trial pursuant to the rule of witness sequestration, OCGA § 24-9-61, while the mother of Tayore was permitted to attend the trial pursuant to a statutory exemption to the rule of sequestration contained in the Crime Victims' Bill of Rights, OCGA § 17-17-9(b). Nicely also claims that the trial court erred when it denied his pretrial demurrer, when it limited his cross-examination of an expert witness at trial, and when it refused to instruct the jury as Nicely requested. Upon our review of the record and briefs, we find no error, and we affirm.1

1. Viewed in the light most favorable to the verdict, the evidence shows that Nicely lived with Shawndia Rogers and her two young children — one of whom was Tayore — in an apartment in Gainesville. On the afternoon of March 30, 2009, Rogers left the apartment for work, leaving the children in Nicely's care. At that time, Tayore appeared to be uninjured and in no distress. About five hours later, Nicely telephoned his aunt and said that Tayore was not breathing. The aunt and a family friend went to the apartment, where they found Tayore unresponsive. Nicely told his aunt that Tayore had fallen down the stairs when he was attending to the other child and that he did not see Tayore fall. The aunt attempted unsuccessfully to revive Tayore, and the family friend called for emergency assistance. Nicely left the apartment before paramedics and other emergency response personnel arrived, and he did not return. The paramedics were able to revive Tayore in the apartment, but the next day, she died in the hospital.

According to Nicely, after he left the apartment, he spent the night sitting "in the dark behind some houses just thinking about what happened." He also made more than 100 telephone and text-message contacts with various friends and relatives, including a cousin to whom he explained that he did not want to go to prison for the rest of his life. The next day, Nicely went to the Gainesville Police Department, where he gave an account of the incident in which Tayore was injured that was inconsistent with the story that he earlier told to his aunt. At the police station, Nicely claimed that he was sliding Tayore down a handrail along the stairs in the apartment when she suddenly jerked out of his grasp, fell over the handrail, and hit her head on the floor below.

At trial, the State called two medical experts as witnesses. Dr. Gerald Gowitt, the Hall County medical examiner, performed an autopsy of Tayore and testified about her injuries. He said that he observed several small bruises on her head and cheeks and that, when he opened her scalp, he observed additional injuries, including multiple blunt-impact sites and hemorrhaging in the forehead and frontal and temporal scalps, as well as a blunt-impact site and hemorrhaging near the back of her head. Moreover, he found swelling in her brain, multiple areas of subdural and subarachnoid hemorrhaging, retinal hemorrhaging, and a schisis cavity in her right eye. Dr. Gowitt testified that the injuries to Tayore were consistent with her having been beaten with a blunt object, and he said that some of the injuries could have been caused by her having been shaken. He also testified that her injuries were inconsistent with a short fall, such as a fall from the handrail in the apartment. Dr. Jordan Greenbaum, medical director at Children's Healthcare of Atlanta's Child Protection Center and a board-certified forensic pathologist, testified that it was "impossible" for Tayore to have sustained her injuries in a short fall. Dr. Greenbaum opined that a violent, repetitive whiplash motion, which could result from a beating or excessive shaking, caused Tayore's death.

In his defense, Nicely called Rogers as a witness, and she testified that Nicely was a good caregiver and had a positive relationship with her children. Nicely also called his father, who testified about praying with Nicely and then taking Nicely to the police station on the morning after the incident in which Tayore was injured. In addition, Nicely presented expert testimony that conflicted with the testimony of Drs. Gowitt and Greenbaum. As we have explained before, however, "[i]t is the role of the jury to resolve conflicts in the evidence and to determine the credibility of witnesses, and the resolution of such conflicts adversely to the defendant does not render the evidence insufficient." Allen v. State, 288 Ga. 263, 264(1), 702 S.E.2d 869 (2010) (citation and punctuation omitted). The evidence in this case was sufficient to authorize a rational trier of fact to find Nicely guilty beyond a reasonable doubt of the crime of which he was convicted. Jackson v. Virginia, 443 U.S. 307, 99 S.Ct. 2781, 61 L.Ed.2d 560 (1979).

2. We turn now to Nicely's contention that his father was denied equal protection when the trial court excluded him from some of the trial proceedings pursuant to the rule of sequestration, but allowed Rogers to attend as the mother of Tayore, notwithstanding that Rogers too was a witness at trial. Known as the rule of sequestration, OCGA § 24-9-61 provides that any party to a trial "shall have the right to have the witnesses of the other party examined out of the hearing of each other."2 See also Williams v. State, 277 Ga. 853, 857(5), 596 S.E.2d 597 (2004). A statutory exemption to the rule appears, however, in the Crime Victims' Bill of Rights:

OCGA § 17-17-9(b). As the mother of a deceased, child victim of the crimes for which Nicely was tried, Rogers was a "victim" of these crimes for the purposes of this statutory exemption. See OCGA § 17-17-3(11)(B)(iii), (C).3 The trial court in this case excluded Nicely's father from the trial until after he testified, but it permitted Rogers to attend even before she testified. Nicely contends that this disparate treatment — the result of the trial court applying the statutory rule of sequestration to the father, and the statutory exemption contained in the Crime Victims' Bill of Rights to Rogers — amounts to a denial of the constitutional guarantee of equal protection.4 We disagree.

Generally speaking, the guarantee of equal protection "is concerned with arbitrary government classification," Engquist v. Oregon Dept. of Agriculture, 553 U.S. 591, 602(II)(B), 128 S.Ct. 2146, 170 L.Ed.2d 975 (2008), and it requires that the law treat similarly situated persons alike, unless adequate reason exists to treat them differently. See id. Accordingly, to show a denial of equal protection, one first must demonstrate that the law treats him differently than similarly situated persons. Fair v. State, 288 Ga. 244, 246(1)(A), 702 S.E.2d 420 (2010). If it is shown that the law, in fact, treats him differently than similarly situated persons, a court then must inquire whether adequate reason exists for doing so. Differential treatment that is based on an inherently suspect classification or that interferes with the exercise of a fundamental right is subject to strict scrutiny, see id., and such treatment ordinarily can be justified only when it is sufficiently related to a compelling state interest. Poulos v. McMahan, 250 Ga. 354, 355, n. 1, 297 S.E.2d 451 (1982). Differential treatment that neither involves a suspect classification nor interferes with a fundamental right, however, is subject to less exacting scrutiny, and it generally can be justified when rationally related to a legitimate state interest. Fair, 288 Ga. at 246(1)(A), 702 S.E.2d 420. See also Rodriguez v. State, 275 Ga. 283, 286(2), 565 S.E.2d 458 (2002).

In support of his contention that his father was denied equal protection,5 Nicely contends that his father and Rogers were similarly situated at his trial, both having a familial interest in the "subject matter" of the trial, one as a parent of the defendant, the other as a parent of the victim. The two quite clearly were treated differently, his father being excluded from portions of the trial, and Rogers being permitted to attend. This differential treatment, Nicely argues, must be subjected to strict scrutiny because it infringes on a fundamental right, namely his own constitutional right to a public trial. And because the State cannot show, he says, that the differential treatment is adequately related to a compelling state interest, it amounts to a denial of equal protection. Even assuming that Nicely has standing to assert an equal protection claim on behalf of his father,6 and assuming that his father and Rogers were similarly situated, we are unpersuaded that his father was denied equal protection.

Whether a right is fundamental for purposes of equal protection generally depends on whether it is "explicitly or implicitly guaranteed by the Constitution," San Antonio Independent School Dist. v. Rodriguez, 411 U.S. 1, 33(II)(B), 93 S.Ct. 1278, 36 L.Ed.2d 16 (1973), and a public trial certainly is guaranteed explicitly by the Sixth Amendment of the United States Constitution. Moreover, the United States Supreme Court has characterized the constitutional right to a public trial as a "fundamental" one, albeit not in the context of an equal protection claim. See Herring v. New York, 422 U.S. 853, 857(II), 95 S.Ct. 2550, 45 L.Ed.2d 593 (1975). See also In re Oliver, 333 U.S. 257, 273, 68 S.Ct. 499, 92 L.Ed. 682 (1948) (federal constitution requires public trials in state criminal proceedings as an element of due process). Nevertheless, the application in this case of the rule of sequestration does not infringe upon that right.

Nicely does not point us to a single case in which the sequestration of a witness was held to violate the right to a public trial, and we have found none. To the contrary, we have found case upon case in which courts have held that the rule of sequestration ordinarily does not even implicate the right to public trial, much less infringe upon it. See, e.g., State v. Jordan, 325 S.W.3d 1, 53(II) (Tenn.2010) ("The sequestration of individual witnesses pursuant to the rule does not threaten any of these interests [that the right to a public trial is meant to safeguard]"); People v. Baker, 14 N.Y.3d 266, 899 N.Y.S.2d 733, 926 N.E.2d 240, 246 (2010) (finding that precedents applying Sixth Amendment principles "have no bearing" on exclusion of potential witness); State v. Ulate, 42 Kan.App.2d 971, 219 P.3d 841, 852 (2009) ("We agree with the State that Ulate's argument is better characterized as a sequestration issue than a Sixth Amendment issue."); Commonwealth v. Jones, 71 Mass.App.Ct. 568, 884 N.E.2d 532, 535(1) (2008) ("We do not view Doyle's exclusion as a closure of the court room [for the purposes of the Sixth Amendment], but rather as the proper exercise of a judge's discretion to order the sequestration of witnesses...."); United States v. Izac, 239 Fed.Appx. 1, 4(II)(B) (4th Cir.2007) (where witness "was subject to exclusion in any event under [rule of sequestration] once the trial began," defendant's "Sixth Amendment right to a public trial was not implicated" by exclusion of witness during jury selection); State v. Peterson, Case No. A05-682, 2006 WL 2129702, *2 (I)(A), 2006 Minn.App. Unpub. LEXIS 821, *5 (I)(A) (Minn.App. 2006) ("The sequestration ruling did not implicate Sixth Amendment guarantees."); State v. Culkin, 97 Haw. 206, 35 P.3d 233, 259(III)(D) (2001) ("[W]e hold the right to a public trial is not implicated by the exclusion of a potential witness pursuant to the witness exclusionary rule."); Tharp v. State, 362 Md. 77, 763 A.2d 151, 160 (2000) (witnesses sequestered under the rule "are no longer considered members of the general public for purposes of exclusion from the courtroom during criminal proceedings, and a criminal defendant's right to a public trial is in no way damaged by proper sequestration...."); State v. Taylor, 244 Ill.App.3d 460, 183 Ill.Dec. 891, 612 N.E.2d 543, 548 (1993) ("Because defendant's mother and stepfather were listed in discovery as potential witnesses, we tend to look upon this issue not as an action by the State which is directed at defendant's [S]ixth [A]mendment right to a public trial, but rather as an act of the parties to exercise a long-standing trial right in criminal cases to request the exclusion of witnesses from the courtroom as part of the usual trial process."); State v. Cyrulik, 100 R.I. 282, 214 A.2d 382, 383 (1965) ("Fundamentally, we think the issue presented here only indirectly raises that of defendant's constitutional right to a public trial and that the basic question before us pertains to the power of the trial court to exclude witnesses from the courtroom."); State v. Cottone, 52 N.J.Super. 316, 145 A.2d 509, 516(IV) (1958) ("The situation here is governed, not by the [state] constitutional provision guaranteeing the right to a public trial ... but by the general rule of judicial discretion applicable to the exclusion of witnesses."); State v. Worthen, 124 Iowa 408, 100 N.W. 330, 331 (1904) ("We do not think the sequestration of the defendant's witnesses infringed upon his constitutional right to a public trial."). At least in the circumstances of this case, we see no infringement of the constitutional right to a public trial by the exclusion of a single witness pursuant to a routine application of the rule of sequestration. Compare Purvis v. State, 288 Ga. 865, 866, n. 3(1), 708 S.E.2d 283 (2011) (finding violation of right to public trial, but noting that brother, who was excluded from trial, "sought to attend the trial `just as a member of the general public,'" not as a witness) (punctuation omitted). We certainly see no infringement sufficient enough to trigger strict scrutiny for purposes of equal protection.

Consequently, the differential treatment of Nicely's father and Rogers passes equal protection muster so long as it is rationally related to a legitimate state interest. Fair, 288 Ga. at 246(1)(A), 702 S.E.2d 420. We think that such a rational relationship exists. The rule of sequestration itself undoubtedly promotes legitimate state interests in, among other things, restraining witnesses from "tailoring their testimony to that of earlier witnesses" and "aid[ing] in detecting testimony that is less than candid." Geders v. United States, 425 U.S. 80, 87, 96 S.Ct. 1330, 47 L.Ed.2d 592 (1976) (citations and punctuation omitted). Likewise, the statutory exemption to the rule contained in the Crime Victims' Bill of Rights promotes legitimate state interests, namely the interest of the State in according to crime victims the same right to be present as the Constitution accords to the accused. See OCGA § 17-17-1. Nicely does not even contend that the differential treatment of his father and Rogers bears no rational relationship to legitimate state interests, and we conclude that it certainly does. For these reasons, the differential treatment of these two witnesses did not work a denial of equal protection.

3. Nicely also contends that the trial court erred when it denied his pretrial demurrer as to the aggravated assault count of the indictment. Nicely argues that the indictment failed to specify the weapon or instrument that he allegedly used to assault Tayore, and he claims that this failure left him unable to prepare an adequate defense. But the trial court entered a judgment of conviction against Nicely, and sentenced him, only for felony murder predicated on cruelty to a child. The trial court merged the aggravated assault and felony murder predicated on aggravated assault counts into the conviction for felony murder predicated on cruelty to a child. Because "merger renders a conviction void, any error as to [the aggravated assault] count is harmless." Black v. State, 309 Ga.App. 880, 883(3), 711 S.E.2d 428 (2011) (citation and punctuation omitted). See also John v. State, 282 Ga. 792, 795(5), 653 S.E.2d 435 (2007) (where felony murder count merged with conviction for malice murder, complaint about jury charge on felony murder was moot).

4. Next, we turn to the contention that the trial court erred and denied Nicely his constitutional right of confrontation when it limited his cross-examination of Dr. Gowitt. More specifically, Nicely asserts that he should have been permitted to cross-examine Dr. Gowitt about an understanding among some Georgia medical examiners that one will not testify "against" the findings of another, an understanding that Dr. Gowitt allegedly has adopted. This line of cross-examination was important, Nicely contends, because Dr. Gowitt relied in part in forming his own opinions on findings by Dr. Greenbaum about the injuries to Tayore, and cross-examination about an understanding among some Georgia medical examiners would tend to show that Dr. Gowitt might have tailored his own opinions and his own testimony to be consistent with the findings of Dr. Greenbaum.7

Although the Sixth Amendment right to confrontation secures the right of cross-examination, Davis v. Alaska, 415 U.S. 308, 315(2), 94 S.Ct. 1105, 39 L.Ed.2d 347 (1974), the right of cross-examination "is not an absolute right that mandates unlimited questioning by the defense." Howard v. State, 286 Ga. 222, 225(2), 686 S.E.2d 764 (2009) (citation and punctuation omitted). To the contrary, trial courts "retain wide latitude... to impose reasonable limits on cross-examination based on concerns about, among other things ... interrogation that is... only marginally relevant." Young v. State, 290 Ga. 441, 444(5), 721 S.E.2d 839 (2012) (citation and punctuation omitted). See also Sanders v. State, 290 Ga. 445, 446(2), 721 S.E.2d 834 (2012). The permissible scope of cross-examination is committed to the sound discretion of the trial court, and we review a limitation of the scope of cross-examination only for abuse of discretion. Hampton v. State, 289 Ga. 621, 626-627(5), 713 S.E.2d 851 (2011). We see no abuse of discretion here.

The trial court permitted Nicely to examine Dr. Gowitt outside the presence of the jury about any understanding among medical examiners, and Dr. Gowitt explained that this understanding would not extend in any event to Dr. Greenbaum, who is not a medical examiner. Moreover, Dr. Gowitt testified unequivocally that he did not feel bound — "legally, ethically, morally, or any other way" — to adopt or accept the findings of Dr. Greenbaum. In these circumstances, the trial court did not abuse its considerable discretion in disallowing cross-examination on any common understanding among some medical examiners.

5. Last, we consider the contention that the trial court erred when it conditioned a jury charge that Nicely requested — a charge on cruelty to a child in the second degree, as a lesser included offense of cruelty to a child in the first degree — upon the giving of another charge that, Nicely says, was improper. The record of the charge conference shows that the trial court was willing to give a charge on cruelty to a child in the second degree, but the trial court indicated that, if it did so, it also would charge the jury that felony murder properly could be predicated on cruelty in the second degree. Nicely argued at trial that cruelty to a child in the second degree could not properly form the basis for felony murder in this case because cruelty in the second degree is not a felony that is "inherently dangerous," and when the trial court disagreed, he withdrew his request to charge on cruelty in the second degree.8

Had Nicely not withdrawn his request to charge, the trial court would have been authorized to give both the requested charge and a charge that felony murder might properly be predicated in this case on cruelty in the second degree. As we have explained before,

Chance v. State, 291 Ga. 241, 242(1), 728 S.E.2d 635 (2012) (citation and punctuation omitted).

Nicely requested a charge on cruelty in the second degree as a lesser included offense based on evidence of his statement to police officers that Tayore fell from a handrail along the stairs as he was sliding her down it. Nicely contends that exposing a child to a short fall — five or six feet — does not create a foreseeable risk of death, pointing to the testimony of Dr. Gowitt in this case that such a fall would rarely result in death. But Dr. Gowitt did not testify that the risk of death from such a fall was unforeseeable, and, in any event, the evidence on the likelihood of death from a short fall was not undisputed. One of Nicely's own experts testified that studies assessing the risk of death from a short fall are unreliable and that, although death might not usually or even commonly result from such a fall, "it is recognized that short distance falls can result in death through subdural bleeding and retinal hemorrhaging." We need not decide, however, whether a risk of a child of tender years falling five or six feet poses a foreseeable risk of death.

Even if we accept that exposure to a short fall does not create such a risk, the evidence authorized the jury to find that Nicely caused the death of Tayore in another way, one that still would warrant a charge on cruelty in the second as a lesser included offense, but that would clearly create a foreseeable risk of death. Cruelty in the first degree and in the second degree both involve causing "cruel or excessive physical or mental pain" to a child. The difference between the two crimes relates to the state of mind of the accused. If one causes such pain maliciously, he commits cruelty in the first degree, OCGA § 16-5-70(b); if he does so with criminal negligence, he commits cruelty in the second degree. OCGA § 16-5-70(c). The State's evidence showed that Tayore had suffered multiple impacts to her head, and the State's theory of the case was that Nicely caused the death of Tayore by striking her on the head or shaking her violently. One of Nicely's own experts testified, however, that it was impossible to know with certainty whether any injuries to her head were caused intentionally or accidentally. Moreover, Rogers testified that Nicely and Tayore had a loving relationship. In the light of this evidence, and because the state of mind of the accused is "peculiarly [a] question[] for the jury," Hinds v. State, 296 Ga.App. 80, 80-81(1), 673 S.E.2d 598 (2009), the jury might properly have found that Nicely committed cruelty in the second degree, not by sliding Tayore down a handrail, but by striking her head against a hard object or shaking her violently with criminal negligence, as opposed to malice. Nicely does not dispute that striking a child on the head or violent shaking is an "inherently dangerous" act. And because the evidence would have permitted (but did not require) a finding that Nicely struck or violently shook Tayore with criminal negligence, not malice, it would have authorized a conviction for felony murder premised on cruelty in the second degree. The trial court did not err when it conditioned the giving of a charge on cruelty in the second degree as a lesser included offense upon the giving of an additional charge that cruelty in the second might form a basis for felony murder.

Judgment affirmed.

All the Justices concur.