San Francisco Chronicle Reports Innocent Man’s DNA was Found at Homicide Scene

DNA has been touted as one of the greatest crime-solving technologies to be developed. But using DNA to identify criminal suspects is not without its problems. Many crimes do not yield themselves to being solved by DNA evidence, and the mere presence of DNA evidence without more, tells us very little about whether or not the person whose DNA was found was actually involved in the criminal act.

DNA is trace evidence. It is genetic material that we leave behind whenever we come in contact with an object or another person. The odds of any two persons having the same DNA genetic sequence is extremely high, though not really as impossible as it might seem. So, finding a person’s DNA  at the scene of a crime, or on the body of a homicide victim, might seem very strong evidence indeed that the person whose DNA was found was the perpetrator of the crime. Even more so, if the person had no other connection or contact with the crime scene to explain how his or her DNA might have been left there innocently.

But there are problems. Consider what happened to 26-year-old Lukis Anderson, who was accused of murder after his DNA was found underneath the fingernails of a homicide victim. Henry K. Lee reports in this San Francisco Chronicle article how DNA was transferred from Anderson, who was picked up at a San Jose Liquor Store by two paramedics and taken to a hospital, to the murder victim several hours later when the paramedics were called to the crime scene and handled the body of the victim.

The first problem is that DNA is easily transferred form one surface to the next. Wipe your face with a towel and you leave DNA on the towel. Wipe another object with that same towel, or another person, and your DNA is transferred to the object or person. The second problem is that technology for amplifying DNA is so powerful that DNA profiles can now be obtained from even exquisitely minute traces of genetic material. That makes the risk of contamination of the DNA sample or the surface from which the sample is taken a serious problem. Contamination can lead to the accusation of an innocent person and possibly a miscarriage of justice and wrongful conviction.

When you consider that in the first 200 DNA exonerations by the Innocence Project, three involved wrongful DNA inclusions at trial, you begin to see the magnitude of the problem. Moreover, one can see how it is that DNA, rather than helping to convict the guilty, can actually work to convict the innocent.