Trace Evidence in Forensic Science
Trace evidence is created when objects come into contact with each other, whether it is the transfer of paint, fingerprints or gunshot residue. They can be removed from a crime scene with various techniques such as tape lifts and swabs. Although trace evidence can link a person to a crime scene, it doesn’t determine their guilt; therefore other corroborating evidence is required.
A number of techniques can be implemented to remove or analysis the trace evidence sample, some being destructive so photographing and measures that are least harmful are utilised as a primary option.
On Saturday 15 August 1998 in Omagh, Northern Ireland, a splinter group of the former Provisional Irish Republican Army who were opposed to the Good Friday Agreement, planted a bomb in a car that killed 29 people and injured some 220 people (The Queen v Sean Hoey  NICC 49).
Trace evidence containing Sean Hoey’s DNA was found on a number of items at the scene of the Omagh Bombing, in addition to several other bomb scenes, using a Low Carbon Number. This allows for DNA evidence to be recovered from crime scenes when the amount of DNA present is “sometimes as small as a millionth the size of a grain of salt” (Buchanan, 2007: n.p.). The downfall of such a sensitive sample is the greater risk of contamination and it is not as robust as conventional DNA testing (Budowie et al, 2009: 207).
DNA evidence means that investigators can link blood, semen, hair or tissue to a single individual, therefore identifying particulars secured at a crime scene can determine possible suspects. It is generally acknowledged that “the potential for false positive results, erroneous matches, is extremely low” (Freckelton, 2010: 21). This enables investigators to narrow down even further the list of suspects connected to a serious crime.
Trace evidence connecting convicted Frank Colledge with the murder of Carolyn Wilden appears to be fairly limited. Shoe prints in blood printed on the mattress stained with Wilden’s blood appears to have been made with thongs found in the rear of the yellow van parked in the backyard’s sleep out. It appears that no fingerprints or DNA of particular interest belonging to Colledge was revealed other than the fact he was a resident of the location in question, which was to later reveal the body of Wilden buried in a shallow grave next to the shed. The case appears to be heavily based on his confession.
To develop footwear impressions in blood, there are 10 techniques that can be used with the more common being Amido Black and Leucocrystal Violet (Saferstein, 2011: 529). The shoe print can be cut out of the fabric and taken to the lab for analysis using either of the two favoured techniques. It can be difficult to prove the offender because the print just shows what type of shoe made the impression and upon finding the shoe, it may be hard to prove the owner, although this may be fairly trivial.
Pamela Lawrence was murdered in her Mosman Park jewellery store in May 1994 and this led to the false conviction and imprisonment of Andrew Mallard. Upon re-examination of the case file in 2006, trace evidence was found in the way of palm print lifts from the glass top service counter at the crime scene in 1994. This was not taken into account at the trial of Mallard, who was convicted based on unsigned police notes and a suspect video recording.
A person’s fingerprint is unique and does not change in the lifetime of the individual. Careful assessment of the ridge characteristics can enable investigators to identify a suspect and place them at a crime scene, although it cannot in any way determine the guilt of the suspect. For two prints to match, they must “reveal characteristics that not only are identical but have the same relative location to one another in a print” (Saferstein, 2011: 391).
The latent prints found on the glass top service counter may have been caused by “the transfer of body perspiration or oils present on finger ridges to the surface of an object” (Saferstein, 2011: 400). After dusting the print with a fingerprint powders and a fibreglass brush, tape lifts can be used which is a method employed to “lift trace particles, extrinsic materials or sebum deposited on the finger of an individual after recent handling of such materials” (Widjaja, 2008: 769).
Trace evidence was found in all three cases although convictions are not always imminent, as seen in the Omagh Bombing. Forensic evidence may assist investigators to identify suspects who may be involved with a crime but cannot prove the guilt of the offender. At times, wrongful conviction may arise out of proceedings, as was the case with Andrew Mallard. Unfortunately, Simon Rochford’s palm print, found on the service counter, was withheld in the investigation that may have prevented Mallard’s false conviction. Although the forensic evidence to link Frank Colledge personally other than a resident of the crime scene was limited, his testimony appeared to have sealed his conviction.
Trace evidence is an important component of forensic evidence and can assist forensic investigators in many ways, although no type of evidence that is more important than another.
Buchanan, M. (2007). Verdict raises DNA evidence doubt. Retrieved from the BBC News Website: http://news.bbc.co.uk/2/hi/uk_news/northern_ireland/7154189.stm
Budowie, B., Eisenberg, A. J., & van Daal, A. (2009). Validity of low carbon number typing and applications to forensic science. Croatian Medical Journal. 50(3), 207
Freckelton, I. (2010). DNA profiling: Collection, use and effectiveness. Melbourne, Victoria: Monash University.
Queen v Sean Hoey  NICC 49
Saferstein, R. (2011). Criminalistics: An introduction to forensic science. Upper Saddle River, New Jersey: Pearson.
Widjaja, E. (2008). Latent fingerprints analysis using tape-lift, Raman microscopy and multivariate data analysis methods. The Royal Society of Chemistry. 134, 769-775.