In a prosecution that led to convictions for murder and related firearms offenses, defendant has not shown that the Superior Court's refusal to give a jury instruction - on the issue of an intervening or superseding cause sufficient to relieve him of responsibility for the death - caused defendant any prejudice, and that refusal was not an abuse of discretion. There was sufficient evidence, including proof of causation, to support the conviction of murder in the first degree, and the trial court did not abuse its discretion by admitting an allegedly prejudicial photograph of the victim's head and shoulders area, displaying the victim's wound, the seriousness of which was highly contested by the parties' experts. While the People made two comments improperly vouching for the veracity of the testimony by the identification witness at trial, in light of the instructions given and the nature of the comments in the context of a multi-day trial, they did not affect the fairness of defendant's trial. The judgment of conviction on the charges is affirmed.