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Expert Blog

Limitations of DNA Evidence: Recent Example

Crime Scene

A recent murder case from the United States has highlighted again the limitations involved when interpreting DNA evidence in a criminal case.

A millionaire was found dead in his mansion near San Jose, California, late last year.  He had been bound and gagged during an apparent home invasion.  His wife had also been beaten but managed to call the police and paramedics (1).   The forensic laboratory found foreign DNA underneath the fingernails of the murdered man.  The foreign DNA profile was loaded onto the DNA database and matched that of 26-year-old Lukis Anderson, a local homeless man.  He was arrested and spent nearly 5 months in prison before it was realised he had an excellent alibi.  At the time of the murder, Mr. Anderson was hospitalized, unconscious and with a blood alcohol reading 5 times the legal limit.

It was then discovered that the same paramedics that conveyed Mr Anderson to the hospital from a liquor store had some 2 hours later attended to the murder scene and attempted to revive the deceased.  It has not yet been elucidated the exact pathway of transfer of the DNA from Mr Anderson to the fingernails of the deceased.  Other individuals have been arrested for the murder.

A DNA profile can now be obtained from as little as 30 or so skin cells.  DNA transfer, whether through direct contact or through an intermediary item or items, is a consideration for every case.  The method of deposition of DNA is less certain when it cannot be related to a visible deposit (such as a blood spatter) or a body fluid such as blood or semen.  Even when it can be related to a body fluid, types of transfer should be considered.  Inadvertent transfer of semen in a hospital examination room led to the 15-month imprisonment of Farah Jama in Victoria for rape in 2008 – when in fact the offence never occurred (2).  Again, the DNA was the only evidence linking the accused to the alleged crime.

  1. San Francisco Chronicle, available at www.sfgate.com
  2. Justice F. Vincent, Inquiry into the circumstances that led to the conviction of Mr Farah Abdulkadir Jama, Victorian Government Printer, Melbourne, Australia, 2010