You have received a package of evidence from a homicide investigation. The victi

Question

You have received a package of evidence from a homicide investigation. The victim was found dead in his own home. There was a possible struggle and the victim was eventually stabbed in the chest (at least 10 times) to death. The police do not have a suspect and are hoping you can develop a foreign DNA profile from the evidence and enter the profile into CODIS. The evidence submitted includes the following items:

victim’s shirt

victim’s fingernail scrapings

bloody knife found in the bushes outside the house

swab of the front door handle (submitted for touch DNA as it was thought the suspect came in through this door).

Based on the scenario, rank these items in order of the most probative item to the least probative item in terms of what is most likely to produce a foreign DNA profile for CODIS entry. Provide your rationale for your order.

You find hairs on the clothing mentioned above. None appear to have roots or follicular tags of epithelial cells. Would you submit these to routine nuclear DNA testing along with your other samples? Explain fully, including your rationale, why or why not?

Explanation / Answer

Answer:

Rank of the items in order of the most probative item to the least probative items are:

1. Victim's fingernail scrapings:

Rationale:

Since there were signs of struggle, there is every possibility of getting skin samples of the suspect in the fingernails of the victim. This would allow enough DNA for DNA profiling.

2. Blood knife found in the bushes:

Rationale:

This evidence can be raked second, next to the victim's fingernail scrapings. There is very high chance of getting touch DNA of the suspect since the suspect had to hold it while commiting the murder. Moreover, since the victim struggled, blood stains corresponding to the suspect may also be found on the weapon if the suspect got wounded in the process.

3. Victim's shirt:

The victim's shirt may contain blood samples and/or hair of the suspect apart from that of the victim if the suspect injured himself during the process (highly probable since there were signs of struggle). In this case, this item will be considered more probative compared to the swab of the front door.

(Skin tissue, blood, hairs or saliva can be left on the victim’s body in case of physical contact)

4. Swab of the front door:

Since the suspect entered through the front door, he might have left touch DNA on the door handle.

Since the hairs did not have the roots/follicles containg epithelial cells, it would not contain any DNA. So, there is no use of submitting these samples for routine nuclear DNA testing.

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