DNA Contamination by Investigators – Cold Case Homicides Highlight Issue

Jane Moira Taupin, Forensic Science Consultant, highlights how the collection of cellular material without knowledge leads to major problems by highlighting a cold case from the United States of America as well as the Claremont serial killings trial. She will be presenting at the upcoming Criminal Law Symposium, where she will discuss what it means to include familial DNA profiling in criminal cases.


Please note that this article reflects information current as of Thursday 27 February 2020.

Contamination of crime exhibits after the incident and through the investigation process has been a reality for many decades.  The increasing sensitivity of DNA techniques means that now a DNA result can be obtained from a few human cells.  The transfer of cellular material from ‘invisible’ deposits is a particular issue in the examination of exhibits from cold cases, which may have been originally collected and examined without knowledge of the ready transfer of detectable DNA.  Two very different cases are discussed to show different aspects of the problem.  One is a recently resolved law suit from the widow of a forensic scientist in the USA, and the other the current ‘trial of the century’ in Western Australia.


Kevin Brown

A young girl Claire Hough had been found murdered and mutilated on a San Diego beach in 1984.  The exhibits were re-examined as part of a cold case inquiry in 2012.  Blood from the girl’s clothing was found to have DNA corresponding to that of Ronald Tatro, a violent convicted rapist.  However, trace amounts of sperm from a medical swab from the victim were found to contain DNA corresponding to Kevin Brown – a former long time employee of the laboratory (1).

Police became fixated on the idea that Tatro and Brown were somehow involved together in the murder even though there was no known connection.  Tatro had drowned in an apparent boating accident in 2011.  During January 2014 a dozen police attended Brown’s home and confiscated 14 boxes and four plastic garbage bags of personal items including thousands of photos and memorabilia from Brown’s wife and her mother.  These items were not returned and ten months later Kevin Brown hanged himself in a tree by a road near a state forest.

Staff DNA samples are taken to detect inadvertent contamination from handling and testing, not as a pool of potential suspects in a crime.  It was common practice for laboratory employees to provide intimate samples such as semen as controls for forensic tests, even up to 2012 in the particular laboratory.  DNA containing material may transfer through examination tools and equipment such as gloves, scissors and magnifying lamps.

The widow of Kevin Brown filed a federal law suit and was recently awarded 6 million dollars in compensatory damages by a judge and a further 50,000 dollars by a jury in punitive damages (2, 3).


Claremont serial killings trial

The cold case investigation of the murder of two young women and the disappearance of a third during 1996 and 1997 in the Perth suburb of Claremont has led to the currently running ‘trial of the century’.  DNA from the accused is alleged to have been found from the fingernails of the deceased Ciara Glennon.  Testing was initially carried out by the state forensic laboratory PathWest in the mid 1990s, and samples sent to New Zealand in 2004.  During 2008 material from two of the fingernails were combined at the now defunct Forensic Science Service in the UK and yielded a male DNA profile using high sensitivity techniques.  The accused was placed under surveillance in late 2016 and a covert DNA sample obtained that was purported to match the male DNA profile from the combined fingernail sample.  Further DNA testing in 2017 and 2018 was performed on the extracts by another UK laboratory Cellmark (4, 5).

The possibility of the crucial fingernail DNA evidence being contaminated has been raised by the defence at the start of the trial.  Four other exhibits in the matter were shown to be contaminated with DNA from PathWest scientists.  An intimate swab from the second deceased Jane Rimmer was analysed by PathWest in 1996 with no male DNA result, but later found in 2017 by Cellmark to have an almost complete profile of a male Pathwest scientist involved in preparing the evidence.  An intimate swab from Ciara Glennon also yielded an almost complete profile of another PathWest scientist involved in testing the exhibit between 1997 and 2001.  Fingernail samples from Jane Rimmer were found by Cellmark to have a DNA profile of another PathWest scientist who was not involved in testing but standing nearby.   Two DNA results from branches at the crime scene of Jane Rimmer tested in 2003 years later yielded DNA of another PathWest scientist who examined them.

The prosecution state that the contaminated samples are not central to their case.  As of writing the trial continues.


DNA contamination

Staff DNA databases are used to detect inadvertent contamination by staff, not as a pool of potential suspects in a crime.  DNA is ubiquitous and contamination can only be mitigated.  It may arise from exhibit to exhibit transfer of DNA from different cases by investigators.  It can occur through collection at the crime scene or medical room, in forensic laboratories including police crime scene and fingerprint laboratories, and from consumables used in DNA analysis (for example the ‘Phantom of Heilbronn’).

Any DNA result must be placed in context.  Investigations where exhibits may have been collected, handled or originally examined without sensitive trace DNA techniques in mind must be treated with caution.


  1. Davis, K., 2017, Judge won’t toss lawsuit accusing San Diego police of driving ex-criminalist to suicide, The San Diego-Union Tribune, 26 May
  2. Wilkens, J., 2020, Trial highlights pitfalls and promise of cold-case DNA evidence, The San Diego Union-Tribune, 8 February
  3. Huard, C., 2020, Widow of SPFD criminalist accused in cold case murder awarded further damages, Times of San Diego, 18 February
  4. Mayes, A., 2020, As with OJ Simpson, the Claremont serial killings case against Bradley Edwards hinges on DNA, ABC News, 18 January
  5. McNeill, H. and Barry, H., 2020, Claremont killer trial Live: Cold case detective reveals details of dramatic early morning arrest of Edwards, Brisbane Times, 25 February

Jane Moira Taupin is an internationally recognised forensic scientist with numerous peer reviewed forensic publications, and author of four forensic texts. She is employed as forensic biology caseworker at Australian and United Kingdom laboratories attending crime scenes and court, and is a specialist in cold cases. She has also presented forensic workshops in Australia, England, Ireland, Qatar and the United States and currently provides forensic expert opinion reviews for criminal and civil cases in Australia, Thailand and the USA. Connect with Jane via LinkedIn