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DNA Actual Case Story

Armed Robbery and DNA Evidence - the face value of evidence is not always what it appears. A good investigative forensic chemist can make a difference.

Case History:
Female assailant allegedly organizes a break in with two other males from another town. She knocks on the door of an alleged drug dealer's apartment home that is shared with at least one other male resident. The two males reportedly stayed behind the female who knocked on the door until the door was opened and then forced their way into the apartment behind the female. Male assailant #1 reportedly possessed a firearm, assailant #2 reportedly possessed a knife. It was reported that there was a struggle between assailant #1 and one of the residents of the apartment, he was struck on the head with the butt of the firearm and restrained with duct tape. The second struggle was between assailant #2 and the other resident of the apartment. During the struggle assailant #2 was struck with the knife he was reportedly carrying whereby drops of blood were able to be found on the floor and on a mirror that was propped up on the floor of the apartment. In the discovery, assailant #2 was reported to have been cut on the face by one statement and on the hand by another statement.

Case Discovery:
Medical records pulled on assailant #2 with reported cut at the scene, had been treated a few weeks earlier for a laceration to the face with sutures. No other reports of being treated for lacerations following the incident. DNA swabs were collected at the scene from blood on the floor and blood on the mirror. Assailant #2 gave DNA saliva sample for comparison. Results from the lab were an exact match without contamination. A forensic toxicologist gave a written report of findings that it was clear and evident that assailant #2 should receive a conviction based on the DNA match.

Considerations and Findings:
Collection of the DNA was not reported to be collected with protective coverings over the face to eliminate cross contamination, nor was it noted that gloves of the collector being changed throughout the evidence collection process, again for elimination of contamination. Collection of DNA evidence can be very frustrating from the contamination aspect because a simple cough, sneeze, spoken words, a wipe of a part of the body of the investigator can very easily contaminate the evidence being collected. The evidence was not reported to be placed in a drying apparatus (standard procedure to eliminate contamination with bacteria) and was reported to have been sealed in the back of the investigators vehicle for approximately twelve days. Additionally, DNA evidence was reported to be collected with a moist swab where the blood collected should have "wicked" through the entire swab, even if the spot was minimal. The drawing (rather than a picture) of the swab done by the crime lab showed only the tip of the swab contained a sample with no apparent wicking according to the drawing. Further assailant #2 had reported that a blood swab sample was collected at the time of arrest. The arresting officer had testified in the co-defendant case that a blood sample may have potentially been take by a nurse via a rape kit, due to the fact that may have been all that was available for a collection. This explained the drawing of the sample in the crime lab report log to me and potentially the evidence was not examined at all and perhaps a mistake in identity of the evidence took place and the swab taken at the time of arrest was now looked at as "evidence" collected.

The report indicated questionable scenarios listed in the considerations and was submitted to the defense attorney of assailant #2. He then presented the report to the ADA with a resolution of no trial necessary. Assailant #1 was charged and sentenced to 27 years. Assailant #2 was dismissed.

Disclaimer: While every effort has been made to ensure the accuracy of this publication, it is not intended to provide legal advice as individual situations will differ and should be discussed with an expert and/or lawyer.For specific technical or legal advice on the information provided and related topics, please contact the author.

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