What piece of evidence would most strongly associate a defendant to a murder victim?

The piece of evidence that would most strongly associate a defendant with a murder victim is the bloodstain found on the defendant's jacket that matches the victim's DNA. This type of evidence is considered highly probative in a murder investigation because DNA provides an almost unique identifier of an individual. When blood is found on a suspect's clothing and it matches the DNA profile of the victim, it indicates a direct biological connection between the defendant and the victim, strongly suggesting involvement in the murder.

In contrast, while a fingerprint found near the crime scene can indicate presence, it does not inherently prove involvement in the act of murder itself, as the fingerprint may not have been deposited during the crime. A witness statement verifying the defendant's presence can be helpful, but witness testimonies can be unreliable or subjective. A photograph of the victim taken prior to the incident does not directly link the defendant to the crime or indicate involvement in the victim's death. Thus, the bloodstain and its matching DNA represent the most definitive form of association between the defendant and the victim, making it the strongest piece of evidence in this context.