DNA clears Cornelius Dupree from 30 years in Texas jail

Jan 5 – A man wrongfully convicted of rape and robbery in the U.S. state of Texas has had his case overturned and has been cleared by DNA evidence after 30 years in jail.

Read more on this case on BBC News, MSNBC, Reuters, Yahoo News.

Gunshot Residue “GSR”

Gunshot Residue (GSR) is a type of physical trace evidence that is released when a gun is fired and may directly place an individual at the scene of weapons discharge.  The inorganic particles are typically found on the hands or clothing of people in the environment and are highly durable heavy metals that form part of the ammunition (Schwoeble and Exline, 2000) .

GSR could be present on the deceased and on the assailants clothing and may be identifiable even if the body is partly or totally decomposed. Clothing is a good medium for the preservation of GSR and it will remain there even if long periods of time have elapsed between the moment of shooting and the time of collection (Schwoeble and Exline, 2000) .

The preservation of clothing obtained at a crime scene and from potential suspects is an important consideration. Care should be taken not to overly handle clothing in order to minimise particle loss (Schwoeble and Exline, 2000) and this highlights the importance for the correct recovery of the evidence at the scene (i.e. by a forensic archaeologist) for further investigation in the laboratory. A misconception that should not be overlooked is, simply because GSR cannot be seen with the naked eye it should not be assumed that it is not there (Schwoeble and Exline, 2000).

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“DNA” trace evidence

The technology for DNA analysis has been greatly improved following the successful mapping of the human genome. Current genetic techniques can determine the identity of an individual with minute amounts of biological material and the approach to genetic sampling and analysis by the forensic pathologist/laboratory worker will depend on the sate of preservation of the remains (Haglund and Sorg, 2002).  It is sometimes possible to gain viable DNA profiles from highly degraded samples that may be old or may have been subjected to outside interference.

Post-mortem blood or tissue DNA analysis may be compared to ante-mortem specimen tests where available, to aid in identification of an individual. It is possible to find mtDNA of maternal lineage present in the mitochondrial organelles of hair so this can also be important for investigations. Any hair found at the site of investigation should therefore be preserved (Dix and Graham, 2000).

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Blood Spatter

It may be possible to associate an assailant to a crime if the clothes they are wearing can be tested for blood.  It has been shown that even dried or decomposed blood can be identified with luminol.  Fine blood spatter is likely to occur from high velocity impact generated from a firearm.  It is possible for an assailant to receive blood spatter on their shoes, trousers, and top including the arm that is holding the weapon. The mist like dispersion of blood droplets typical of a high velocity impact is not likely to reach further than about 4 feet and ultimately the amount of blood spatter will depend on the location of the assailant with regards to the victim (James and Eckert, 1999).