O.J. Simpson’s defense pulled out its strongest weapon against DNA evidence Wednesday with an expert’s testimony that the police DNA lab is infected with chronic contamination that casts doubt on all its test results.
Denver microbiologist John Gerdes said he also found sloppiness so serious at the Los Angeles Police Department lab that it could have allowed foreign DNA to be introduced into evidence samples.
“I found that the LAPD lab has a substantial contamination problem that is persistent,” Gerdes told jurors. “It is chronic in the sense that it doesn’t go away. It’s there month after month, and it doesn’t go away.”
Gerdes testified that he has examined 23 DNA laboratories across the country.
Asked if the level of contamination at the LAPD lab was “worse than in any other forensic laboratory” he has seen, Gerdes replied: “Definitely, by far.”
The witness gave jurors specific examples of LAPD sloppiness in the Simpson case. He noted that a lab technician handled Simpson’s blood sample at the same time he was handling a bloodstained glove in evidence.
“The rules are, you never handle a reference sample at the same time as any other evidence,” Gerdes said.
He showed jurors pictures of the lab, noting test tubes were stored touching each other, risking cross-contamination, and a bottle of chemical solution used in DNA testing was labeled with a date that was four months old. He said other labs replace such solution every week to avoid contamination.
Gerdes said overall results of DNA tests in the case suggested cross-contamination of blood samples from Simpson and victims Nicole Brown Simpson and Ronald Goldman.
Gerdes tried to cast doubt on prosecutors’ suggestion that Goldman’s blood was found mixed with Simpson’s blood on the console of Simpson’s Ford Bronco. He said a prosecution scientist could have mistakenly identified one of Goldman’s genetic markers in the blood mix.
“Are there any other results consistent with Mr. Goldman’s genotype (in the Bronco?)” defense attorney Barry Scheck asked.
“No,” Gerdes replied.
The prosecution has relied heavily on DNA technology to link Simpson to the June 12, 1994, murders.
Defense attorneys have responded by attacking police scientific techniques, saying no test results should be trusted. The defense also has accused police of planting evidence to frame the former football star.
Gerdes suggested the LAPD system was so filled with errors that technicians should have become “paranoid” about their test results, shut down their system and cleaned it out at some point.