Wright, J.
We are required by R.C. 2929.05(A) to undertake a three-prong analysis in all death penalty cases. First, we must review each of the nine propositions of law raised by appellant. Second, we must independently review the record to determine whether the aggravating circumstances outweigh the mitigating factors. Finally, we must independently determine whether the sentence of death is excessive or disproportionate to the penalty imposed in similar cases. For the reasons set forth below, we reverse the court of appeals in part, and affirm the convictions and sentence of death.
In Proposition of Law II, appellant contends that the jury verdict was improper because it did not indicate that the jury unanimously found either that he was the principal offender in the murder or that he acted with prior calculation and design. . We first note that appellant did not timely object to the verdict forms and thus waived all but plain error. Moreover, each of the verdict forms which the jury used and signed contained language, conforming to the statute, stating either that Williams was the principal offender, or that Williams had committed the murder with prior calculation and design. See R.C. 2929.04(A)(7); see State v. Penix (1987), 32 Ohio St.3d 369, 513 N.E.2d 744.
Appellant also contends as part of Proposition of Law II that the trial court should have instructed the jury on the law of aiding and abetting. This argument is without merit. As the person who performed every act constituting the aggravated murder, Williams was the principal offender. State v. Sneed (1992), [574] 63 Ohio St.3d 3, 12, 584 N.E.2d 1160, 1168. It was therefore unnecessary for the court to instruct the jury on aiding and abetting.1 We find that Proposition of Law II lacks merit.
In Proposition of Law IX, appellant contends that the trial court erred because it did not instruct the jury on the lesser included offense of involuntary manslaughter. Involuntary manslaughter is a lesser included offense to aggravated murder. State v. Thomas (1988), 40 Ohio St.3d 213, 533 N.E.2d 286, paragraph one of the syllabus. We find that the trial court did not err by refusing to instruct the jury on involuntary manslaughter because a charge on a “lesser included offense is required only where the evidence presented at trial would reasonably support both an acquittal on the crime charged and a conviction upon the lesser included offense.” Id. at paragraph two of the syllabus.
Here, under any reasonable view of the evidence, Williams was the principal actor in the purposeful killing of Mr. Melnick. If the defense had argued that Williams was a bystander or that the killing was not purposeful, an instruction on involuntary manslaughter would have been necessary. As it was, the defense contended that Williams was not present at the crime. Thus, on the evidence presented, the jury could not have found Williams not guilty of aggravated murder and guilty of involuntary manslaughter. Accordingly, the trial court’s failure to instruct on involuntary manslaughter was not error.
Furthermore, the injuries that Mr. Melnick suffered do not reasonably permit a finding that he was not killed purposefully. In Thomas, this court stated, “It is axiomatic that ‘a person is presumed to intend the natural, reasonable and probable consequences of his voluntary acts.’ ” Id., 40 Ohio St.3d at 217, 533 N.E.2d at 290, quoting State v. Johnson (1978), 56 Ohio St.2d 35, 39, 10 O.O.3d 78, 80, 381 N.E.2d 637, 640. Further, Williams told several people that he had beaten and robbed an elderly couple on Wick Street, giving details of the assault, and was overheard saying that he had killed the man. When speaking to Jennifer Gunther and Lance Owens, Williams actually demonstrated what he had done during the killing. Thus, in this case, “no reasonable jury could have both rejected a finding of guilty on the charged crime and returned a verdict of guilty on the lesser included offense of involuntary manslaughter.” State v. Shane (1992), 63 Ohio St.3d 630, 633, 590 N.E.2d 272, 275. See State v. Campbell (1994), [575] 69 Ohio St.3d 38, 47-48, 630 N.E.2d 339, 349, We find that Proposition of Law IX lacks merit.
In Proposition of Law V, appellant claims that a crime scene video and gruesome, inflammatory, and duplicative photographs prejudiced his right to a fair trial. The defense timely objected to the photographs. However, the defense did not timely object to the final edited version of the video and thus waived all but plain error with respect to that issue. State v. Williams (1977), 51 Ohio St.2d 112, 5 O.O.3d 98, 364 N.E.2d 1364.
Under Evid.R. 403 and 611(A), the admission of photographs is within the trial court’s sound discretion. State v. Landrum (1990), 53 Ohio St.3d 107, 121, 559 N.E.2d 710, 726; State v. Maurer (1984), 15 Ohio St.3d 239, 264, 15 OBR 379, 401, 473 N.E.2d 768, 791. Nonrepetitive photographs are admissible in capital cases, even if they are gruesome, when the probative value of each photograph outweighs the danger of material prejudice to the accused. Id. at paragraph seven of the syllabus; State v. Morales (1987), 32 Ohio St.3d 252, 258, 513 N.E.2d 267, 273-274. In this case, the trial court did not abuse its discretion in admitting the objected-to photographs because none of them was repetitive and each photograph’s probative value outweighed its prejudicial impact.
Six of the objected-to photographs depicted separate injuries to Mr. Melnick’s head. One of the other photographs depicted defensive-type wounds on Mr. Melnick’s arm, and another showed leg wounds. Collectively, the photographs illustrated and corroborated the testimony of the coroner and the police officers. The photographs also depicted the nature and severity of the wounds and were thus probative of the killer’s intent to kill. The trial court closely examined every proffered photograph and in fact excluded several. There was no abuse of discretion with respect to these photographs.
As to the final edited version of the videotape, the defense failed to object at trial and thus waived all but plain error. Since nothing in the record suggests that the verdict would have clearly been otherwise if the videotape had not been admitted, there was no plain error. See State v. Underwood (1983), 3 Ohio St.3d 12, 3 OBR 360, 444 N.E.2d 1332, syllabus.
In Proposition of Law VIII, appellant makes three arguments with respect to the jury’s finding that Williams was guilty of attempted rape. Appellant argues that the prosecutor asked an expert witness improper and prejudicial questions, that the trial court erred in denying defense counsel’s Crim.R. 29 motion for acquittal, and that the trial court improperly charged the jury on the lesser included offense of attempted rape. We address each of these arguments separately.
The prosecutor asked criminalist Dale L. Laux, “[I]n your experience, training and analysis, have you had an occasion to analyze rape kits in alledged [sic] [576] rapes where there was no presence of semen or seminal fluid?” Though the question is arguably inartful, we find that the prosecutor’s question in no way prejudiced Williams. In his answer, Laux expressed no opinion on the ultimate issue of whether a rape occurred. He merely observed that the absence of semen does not prove that a rape did not occur. Further, Laux stated that he found “no physical evidence of a rape” on Mrs. Melnick. We reject the argument that the trial court erred by not excluding this question.
The admission of expert testimony is within a trial court’s discretion. State v. Williams (1983), 4 Ohio St.3d 53, 4 OBR 144, 446 N.E.2d 444, syllabus. An expert opinion is admissible when it “dispels a misconception common among lay persons.” Evid.R. 702(A). Thus, because jurors might mistakenly ascribe greater significance to the absence of semen than warranted, the trial court exercised sound discretion in allowing Laux to answer.
With respect to appellant’s argument that the trial court improperly rejected the Crim.R. 29 motion for acquittal, the “relevant inquiry is whether, after viewing the evidence in a light most favorable to the prosecution, any rational trier of fact could have found the essential elements of the crime proven beyond a reasonable doubt.” State v. Jenks (1991), 61 Ohio St.3d 259, 574 N.E.2d 492, paragraph two of the syllabus, following Jackson v. Virginia (1979), 443 U.S. 307, 99 S.Ct. 2781, 61 L.Ed.2d 560. We believe there was sufficient evidence of forcible sexual conduct in the record to allow a rational fact finder to find Williams guilty of attempted rape.
Mrs. Melnick had been beaten and was found lying in a pool of her own blood, with her underwear on the floor beside her. She remembered nothing about the attack other than that she had been wearing underwear immediately before the attack. Lance Owens, Henry Daniel, Jr., Ruben Gunther and Mario Daniel, all testified that Williams had told them about raping Mrs. Melnick. Given this evidence and testimony, it is certainly possible that a “rational trier of fact could have found the essential elements of the crime proven beyond a reasonable doubt.” Jenks, 61 Ohio St.3d 259, 574 N.E.2d 492, paragraph two of the syllabus. Thus, a jury could reasonably find that Williams attempted to rape Mrs. Melnick. See State v. Scudder (1994), 71 Ohio St.3d 263, 274-275, 643 N.E.2d 524, 533; State v. Durr (1991), 58 Ohio St.3d 86, 92-93, 568 N.E.2d 674, 681-682. It should also be noted that Williams was acquitted of rape, rendering the Crim.R. 29 motion on that charge moot. We reject the argument that the trial judge improperly overruled the Crim.R. 29 motion.
The court of appeals reversed appellant’s conviction under Count Three, finding that “there was no evidence to suggest that Appellant formed his intent to rape Katherine Melnick prior to the time that he inflicted his fatal assault on George Melnick.” In Proposition of Law I of its cross-appeal, the state contends [577] that the court of appeals’ finding resulted from an erroneous interpretation of State v. Rojas (1992), 64 Ohio St.3d 131, 592 N.E.2d 1376. The court of appeals stated:
“[Rojas ] established that for purposes of R.C. 2903.01(B) and R.C. 2929.04(A)(7), it is necessary that evidence be presented from which a fact finder could reasonably conclude that the defendant formed his intent to commit the underlying felony prior to or during the commission of the acts which resulted in the murder victim’s death.”
The state contends that the evidence “need not establish that an offender formed an intent to commit an attempted rape at or prior to the time” he committed the murder. Rather, R.C. 2929.04(A)(7) requires that the murder occur “while the offender was” committing a felony, attempting to commit a felony, or fleeing from the scene of a felony. The trial court correctly instructed the jury that the term “while” “means that the death must occur as part of acts leading up to, or occurring during, or immediately subsequent to the [relevant felony].”
The Rojas decision itself supports the state’s argument on this issue. Rojas did not rob his victim until hours after he had stabbed her and the case reflects that he did not stab her in order to rob her. State v. Rojas, 64 Ohio St.3d at 131-132, 592 N.E.2d at 1379. In this case, each of the crimes of which Williams was convicted occurred during one continuous incident. Accordingly, Williams should not be able to escape the felony-murder rule by claiming the rape was merely an afterthought. See State v. Smith (1991), 61 Ohio St.3d 284, 290, 574 N.E.2d 510, 516.
. This court has had occasion to explain the meaning of the word “while” with respect to R.C. 2903.01(B), stating:
“ ‘The term “while” does not indicate * * * that the killing must occur at the same instant as the attempted rape, or that the killing must have been caused by the attempt, but, rather, indicates that the killing must be directly associated with the attempted rape as part of one continuous occurrence * * *.’ * * * The evidence here showed that the murders were associated with the kidnappings, robbery, and rapes ‘as part of one continuous occurrence.’ ” State v. Cooey (1989), 46 Ohio St.3d 20, 23, 544 N.E.2d 895, 903, quoting State v. Cooper (1977), 52 Ohio St.2d 163, 179-180, 6 O.O.3d 377, 386, 370 N.E.2d 725, 736.
In this case, the murder of Mr. Melnick was “associated” with the attempted rape of Mrs. Melnick “as part of one continuous occurrence.” As such, this case satisfies the Cooey test. The facts are even stronger than those in Rojas and Smith, in which death sentences were affirmed, because there is no evidence which suggests a substantial passage of time between the assault on Mr. Melnick and the attempted rape of Mrs. Melnick. Thus, we find that neither the felony-[578] murder statute nor Ohio case law requires the intent to commit a felony to precede the murder in order to find a defendant guilty of a felony-murder specification. In doing so, we reject the court of appeals’ interpretation of R.C. 2903.01(B) and 2929.04(A)(7).
Appellant’s final argument within Proposition of Law VIII is that the trial court improperly instructed the jury on attempted rape. We reject this contention because the crime of attempted rape, which is a lesser included offense of rape, was raised by the evidence. See State v. Thomas, 40 Ohio St.3d 213, 533 N.E.2d 286, paragraph two of the syllabus. Moreover, the defense requested an instruction on attempted rape, and cannot now complain of any error so induced. See Crim.R. 30(A); State v. Seiber (1990), 56 Ohio St.3d 4, 17, 564 N.E.2d 408, 422.
In Proposition of Law I, appellant argues that the court of appeals lacked the authority to affirm his death sentence by reweighing the evidence because the court of appeals found that some mitigating evidence had been improperly excluded by the trial court. We reject this argument.
Independent appellate reweighing has been upheld in varied situations and “does not contravene the role of the jury in the penalty proceeding.” State v. Holloway (1988), 38 Ohio St.3d 239, 527 N.E.2d 831, paragraph two of the syllabus; see State v. Combs (1991), 62 Ohio St.3d 278, 286, 581 N.E.2d 1071, 1079; State v. Landrum, 53 Ohio St.3d at 115, 559 N.E.2d at 721. Rather, in a death penalty case, the true purpose of independent appellate review is to provide “a procedural safeguard against the arbitrary imposition of the death penalty.” Holloway, 38 Ohio St.3d 239, 527 N.E.2d 831, paragraph two of the syllabus. Appellate reweighing requires the court to consider proffered evidence that the jury was erroneously not allowed to consider. Thus, any deficiency in the lower court’s decision can be cured by the reviewing court’s independent sentence assessment. State v. Simko (1994), 71 Ohio St.3d 483, 493, 644 N.E.2d 345, 354; State v. Green (1993), 66 Ohio St.3d 141, 149, 609 N.E.2d 1253, 1260. Accordingly we reject Proposition of Law I.
The testimony that the trial court excluded was that of attorney R. Scott Krichbaum. The defense wanted him to testify, as an expert, regarding whether Williams lacked a “significant history of prior criminal convictions” pursuant to R.C. 2929.04(B)(5). (The parties had stipulated to Williams’s criminal record.) The court of appeals held that excluding the proffered testimony was error. We reverse that holding.
Whether an accused’s criminal history is “significant” under R.C. 2929.04(B)(5) is a jury question. The weight to be given such a conclusion is also a question for the jury. The trial court simply exercised its discretion “to refuse to admit the testimony of an expert witness on an ultimate issue where such testimony is not [579] essential to the jury’s understanding of the issue and the jury is capable of coming to a correct conclusion without it.” Bostic v. Connor (1988), 37 Ohio St.3d 144, 524 N.E.2d 881, paragraph three of the syllabus. As there is no legal standard to determine the “lack of a significant history of prior criminal convictions,” the significance of Williams’s criminal history under R.C. 2929.04(B)(5) does not involve professional matters “requiring special study, experience or observation not within the common knowledge of laymen[.]” McKay Machine Co. v. Rodman (1967), 11 Ohio St.2d 77, 40 O.O.2d 87, 228 N.E.2d 304, paragraph one of the syllabus.
The jury knew of Williams’s criminal record and was properly instructed with respect to mitigating factors by the trial judge. The jury thus had all the information necessary to properly evaluate this asserted mitigating factor. “Expert” testimony on such an issue would have been improper. We find that whether a person has a “significant history of prior criminal convictions” under R.C. 2929.04(B)(5) is a question for the jury and is specifically outside the province of expert testimony.
In Proposition of Law III, appellant contends that the trial court erred because it did not merge the four separate death penalty specifications charged against Williams for sentencing purposes. As the defense failed to object at trial, it waived all but plain error. Thus, the defense must, but did not, establish that “the outcome of the trial clearly would have been otherwise” if the asserted error had not occurred. State v. Long (1978), 53 Ohio St.2d 91, 7 O.O.3d 178, 372 N.E.2d 804, paragraph two of the syllabus. Moreover, Williams waived the issue by not raising it before the court of appeals. State v. Williams (1977), 51 Ohio St.2d 112, 5 O.O.3d 98, 364 N.E.2d 1364. Despite the waiver of this issue, we will address it briefly.
The defense’s argument is based primarily on this court’s decision in State v. Jenkins (1984), 15 Ohio St.3d 164, 15 OBR 311, 473 N.E.2d 264, paragraph five of the syllabus. In Jenkins, the defendant was charged with five specifications, three of which alleged that he committed aggravated murder (1) to escape apprehension for aggravated robbery, (2) while committing or fleeing after committing aggravated robbery, and (3) while committing or fleeing after committing kidnapping. This court held that specification (1) unnecessarily duplicated (2), and that specification (2) unnecessarily duplicated (3). The specifications were duplicative because they were part of an indivisible course of conduct. Accordingly, the specifications were merged. Id. at 194-195, 15 OBR at 337-340, 473 N.E.2d at 292-295.
In this case, the felony-murder and multiple murder specifications represent distinct and separate aggravating circumstances and therefore are not duplicative. See State v. Frazier (1991), 61 Ohio St.3d 247, 256, 574 N.E.2d 483, 490-[580]*580491. Aggravated burglary and aggravated robbery are separate offenses and constitute separate aggravating circumstances because they do not arise from the same act. See State v. Slagle (1992), 65 Ohio St.3d 597, 611, 605 N.E.2d 916, 929; State v. Barnes (1986), 25 Ohio St.3d 203, 207, 25 OBR 266, 269-270, 495 N.E.2d 922, 925. Under the facts of this case, attempted rape is also a separate offense and aggravating circumstance because it involves separate offense elements and an animus separate from the aggravated burglary and aggravated robbery. Accordingly, even in the absence of waiver, we would reject Proposition of Law III because the death penalty specifications were not duplicative.
In Proposition of Law IV, appellant argues that the prosecutor improperly referred to Williams’s failure to testify at the sentencing hearing. During his closing argument at the sentencing hearing the prosecutor said, “Finally the last person presented in the penalty phase of this case was the Defendant. * * * Every witness who’s testified as to what happened in this case took that witness stand under oath and told you what happened. Every witness except one. The Defendant.” The setting of the comments and the context indicate that the prosecutor’s comments were directed to the unsworn statement made by Williams at the sentencing hearing. However poorly crafted the comments may have been, they were not directed to Williams’s failure to testify at trial. Consequently, the prosecutor’s comments were not improper and we reject Proposition of Law IV. State v. DePew (1988), 38 Ohio St.3d 275, 528 N.E.2d 542, paragraph two of the syllabus; State v. Lewis (1993), 67 Ohio St.3d 200, 206-207, 616 N.E.2d 921, 926; State v. Coleman (1989), 45 Ohio St.3d 298, 301, 544 N.E.2d 622, 627.
In Proposition of Law VI, appellant argues that when the trial court reviewed the jury’s recommendation for the death penalty it improperly considered the facts and circumstances of the case itself, as what the appellant terms “a non-statutory aggravating circumstance.” To the contrary, the trial court accurately identified, and the jury found, four specified aggravating circumstances. When a court so finds, there is a presumption that it relied only on those specified aggravating circumstances and that it did not rely on nonstatutory aggravating circumstances. State v. Rojas, 64 Ohio St.3d at 142, 592 N.E.2d at 1386; State v. Wiles (1991), 59 Ohio St.3d 71, 89, 571 N.E.2d 97, 120. We find that the trial judge did not improperly rely on nonstatutory aggravating factors and accordingly reject Proposition of Law VI.
In Proposition of Law VII, appellant challenges the constitutionality of Ohio’s death penalty statute. This challenge is summarily rejected. State v. Poindexter (1988), 36 Ohio St.3d 1, 520 N.E.2d 568, syllabus; State v. Jenkins, 15 Ohio St.3d 164, 15 OBR 311, 473 N.E.2d 264.
We find that the evidence supports a finding of the aggravating circumstances charged against Williams beyond a reasonable doubt. We therefore agree with [581] the jury that Williams killed Mr. Melnick while committing aggravated burglary, aggravated robbery, and attempted rape, R.C. 2929.04(A)(7), and as a “course of conduct” with intent to kill two or more, R.C. 2929.04(A)(5).
Some mitigating factors are present in this case. Williams has a low IQ, which was recognized by authorities who attempted to provide help and assistance. However, no evidence at trial established that Williams’s low IQ caused him to lack the “substantial capacity to appreciate the criminality of his conduct” or “conform” to the law. Williams was raised by a grandmother who loved, supported and nurtured him. He was twenty-one at the time of the offense.
We believe that Williams can also qualify for the R.C. 2929.04(B)(5) mitigating factor, “lack of a significant history of prior criminal convictions[.]” His two 1987 assault convictions and his 1988 shoplifting conviction diminish the significance of this mitigating factor. We find that since Williams personally killed Mr. Melnick, he fails to qualify for the R.C. 2929.04(B)(6) mitigating factor. None of the mitigating factors in R.C. 2929.04(B)(1) and (2) appears applicable, since no evidence suggests that the victims induced the offense or that Williams acted under “duress, coercion, or strong provocation.” No “other factors,” R.C. 2929.04(B)(7), are applicable. While we recognize that some mitigating factors are relevant to this case, we find that the aggravating circumstances outweigh the mitigating factors.
The sentence of death is proportionate when compared with similar felony-murder cases. See State v. Slagle, 65 Ohio St.3d 597, 605 N.E.2d 916; State v. Murphy (1992), 65 Ohio St.3d 554, 605 N.E.2d 884; State v. Rojas, 64 Ohio St.3d 131, 592 N.E.2d 1376; State v. Smith, 61 Ohio St.3d 284, 574 N.E.2d 510; State v. Lott (1990), 51 Ohio St.3d 160, 555 N.E.2d 293; State v. Holloway, 38 Ohio St.3d 239, 527 N.E.2d 831; State v. Barnes, 25 Ohio St.3d 203, 25 OBR 266, 495 N.E.2d 922. In addition, the death sentence in this case is proportionate when compared with prior “course of conduct” murder cases. See State v. Dunlap (1995), 73 Ohio St.3d 308, 652 N.E.2d 988; State v. Loza (1994), 71 Ohio St.3d 61, 641 N.E.2d 1082; State v. Grant (1993), 67 Ohio St.3d 465, 620 N.E.2d 50; State v. Lorraine (1993), 66 Ohio St.3d 414, 613 N.E.2d 212; State v. Hawkins (1993), 66 Ohio St.3d 339, 612 N.E.2d 1227; State v. Montgomery (1991), 61 Ohio St.3d 410, 575 N.E.2d 167; and State v. Combs, 62 Ohio St.3d 278, 581 N.E.2d 1071, including cases cited at 294, 581 N.E.2d at 1084.
We affirm the convictions and death penalty sentence and reverse on the cross-appeal.
Judgment affirmed in part and reversed in part.
Moyer, C.J., Douglas, Resnick, F.E. Sweeney, Pfeifer and Cook, JJ., concur.