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Forensic DNA: Who is Lying?


Nobel laureate Kary Mullis views the slippery slope of applied DNA amplification

Kary Mullis is vice president for molecular biology at Burstein Technologies and consults for other companies on nucleic acid chemistry. He won the Nobel Prize and the Japan Prize in 1993 for inventing PCR.

Sitting in a Queensland courtroom a week ago, I was glancing over my shoulder at Wayne Edward Butler, a mild-mannered defendant charged with murdering a woman in August of 1983 on a small island off the tropical east coast of Australia. She was violently struck on the head while sunbathing nude on the secluded, no-witness beach. Mr. Butler was alleged to have foolishly left his DNA signature in the form of several droplets of semen on her large red towel, and that was the only real evidence against him.

No one knew that an unknown biochemist was, just that month in Emeryville, Calif., setting up the first little purple-capped experiment that was going to become the polymerase chain reaction.

The towel sat in a plastic bag in an un-airconditioned warehouse until years later, when the John Tonge forensic center in Brisbane purchased PCR equipment.

I divided my attention between Mr. Butler and Mr. Leo Freney, the forensic pathologist on the stand. The evidence sounded matter of fact and, with the exception of the expert witnesses on either side, it could have been Greek to all others in Her Majesty’s courtroom.

The details read like the pages of a lab notebook, penned by technicians. In a week, Wayne Edward Butler would be doing life, and the forensic pathologist would be doing fine, a new feather in his prosecutorial cap. Maybe deserved, maybe not.

I was there to understand the testimony professionally from inside the circle of DNA chemistry. I was there to make sure the evidence had been properly collected and preserved from contamination. Most importantly, it should have been preserved from the DNA of the known blood sample of the defendant taken from him while in custody. When the prosecution delivered the odds of ten to the fourteenth that this was their man, it would be of paramount importance that they had played fair, and weren’t just comparing the little electrophoretic bands from the defendant’s blood with bands generated somehow from that same tube of blood.

What I saw playing out in this Greek drama in Brisbane was that which so often plays itself out in a murder case: the defendant swears that he is innocent, and the representatives of the state swear that their evidence against him is beyond reproach. Regardless of how many exact-sounding numbers are presented, it is hard to tell who is telling the truth. Someone has to be mistaken or lying.

You can look at the notes from the lab, you can listen to the defendant’s statements, but you can’t go back in time, in spite of how much you yearn to. You can suspect that the defendant is lying. It’s customary. But you can also suspect that the forensic pathologist is lying — or that an ambitious technician made a "mistake." There is every reason to be as wary about the lab as the defendant, because both benefit from a victory. The lab less than the defendant, but over the long run and many cases, victories add up for the lab. You want to buy some new equipment? You need some new employees? A raise? What have you done for us?

In Queensland, the lab is officially independent of the Crown, but as anywhere, there are interactions. There are many newspaper articles attached to the walls of the office of the director of this lab and none of them describes cases that he lost. The director and the police may take a "cleansing ale together" after a case like this. They are certainly better friends than either is with the defendant. Somebody pays the lab’s bills, and it’s not the defendant. It’s the government, and the government is the prosecution.

Before the world settles on this scientific system for determining guilt, something needs to be done. The process needs to be made scientific with real controls.

There is a way to scientifically deal with reference blood, and that it is not done is totally baffling. It is called a taggant, and it has been mentioned more than once in places where the world’s forensic pathologists have heard it.

When a sample of blood is taken from a suspect, in the presence of his lawyer, some substance, easily analyzable, must be put into the tube at the same time — something that can never be obliterated without removing the human DNA itself. A simple first guess would be a DNA sequence contained between two primer sites that could always be amplified and detected. These days it could be sequenced very economically. It could be similar to the EDTA that was found in the blood from the Bundy gate in the O.J. Simpson trial, only better. It would clearly state in a code that a courtroom could understand: “The human DNA in this sample was drawn from the arm of suspect X on date Y by technician W in the presence of lawyer Q.” No one would ever be convicted again on the basis of his own offered DNA being found in the evidence.

Synthetic DNAs, even imbedded in large plasmids to give them physical properties more resembling human DNA, are infinitely cheap compared to months of lawyers, days of court time, and the rest of somebody’s life.

Thousands of court hours that are every month devoted to evidence of DNA contamination, hours which often come down to “Who is lying?”and can never really be objectively decided, could be dispensed with.

The bad guys could go to jail and the innocent victims could go home. No one would be the lesser for it.

Opposite Strand is a forum for readers to express opinions and ideas about trends and issues in genomics. Submissions should be kept to 550 words and may be submitted to [email protected]

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