The revelation of a long-kept secret pointed investigators to the two men now accused of murdering seven people at a Palatine fast-food restaurant. But authorities made clear Saturday that it was an advancement in DNA science that gave them their biggest break.
When Palatine police found a partially eaten chicken at the Brown’s Chicken & Pasta crime scene on Jan. 9, 1993, the technology for identifying who ate the meal was still poorly developed. But investigators held tight to the potential evidence and stored it in a freezer.
On May 9, scientists at the Illinois State Police crime lab used DNA analysis to match saliva taken from a chicken bone to the DNA profile of Juan Luna, one of the two suspects now charged with murder.
Forensic experts said it was fortunate that authorities in the Brown’s case had the presence of mind to freeze the chicken samples for tests that were still on the drawing board.
Investigators praised
“It shows they were pretty forward-thinking, whoever decided to save it,” said David Coffman, supervisor of Florida’s DNA database. “Ten or even seven years ago, we would never have thought to test a piece of food that was half-eaten. We wouldn’t have had the technology to get a result.”
Palatine Police Chief John Koziol underscored that point at a Saturday news conference. “Frankly, the technology was not there,” he said. But in late 1999, “we had them take another look at the chicken.”
The basic techniques for amplifying tiny amounts of DNA evidence–called PCR–had been around since 1985. The techniques for reliably coding and analyzing genetic evidence were first proposed in 1992, then the crucial technology was gradually refined and gained acceptance in the years after the Brown’s Chicken murders.
But by 1993, when the murders were committed, it already was clear to some in law enforcement that DNA fingerprinting would soon become a powerful crime-solving tool. Koziol, in fact, said Saturday that his department had been “somewhat familiar with DNA profiling” because of an earlier case of a newborn baby found drowned in Salt Creek.
“That’s why we saved” the chicken, Koziol said.
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Before PCR became widely available, tests of saliva or blood typically required a stain at least the size of a dime, experts said. But PCR can make almost unlimited copies from minute traces of DNA, allowing police to work with samples the size of a pinhead.
“New DNA tests allowed us to look at much smaller evidence,” said Jim Kearney, head of the Illinois State Police crime lab in Chicago, during Saturday’s news conference in Palatine. “We were able to extract from those chicken bones a solid DNA profile.”
In mid-April, police took DNA samples from Luna and the other man charged, Jim Degorski. On May 9, Kearney said, “we were able to match the profile from Juan Luna with the profile from the chicken bone.”
The technique for making such a match dates to about 1995, when Canadian forensic experts were perfecting the first reliable DNA identification using STRs–or short tandem repeats. Those repeats are stretches of DNA that vary from person to person.
In 1998, the Federal Bureau of Investigation released national standards that use 13 different STR markers to match genetic material with suspects. Using so many markers makes it unlikely that a match using such methods is due to chance. Also in 1998, the FBI launched a nationwide criminal DNA database, increasing the incentive for states to use the technology.
Freezing the sample
Obtaining samples such as those used in the Brown’s case involves freezing the food, then taking a swab with a Q-tip dampened with distilled water.
“Freezing the food makes it firmer, so it’s easier to swab,” said Jean Roney, head of the biology section for the Saskatchewan office of the Royal Canadian Mounted Police.
So long as the samples have been stored in a cold place, the DNA can persist intact for decades or longer, experts said.
Genetic material from the chicken would not contaminate the test, Roney said, because the DNA tests that most labs use are capable of analyzing only human DNA.
Just last week, such DNA techniques were the center of debate in the Illinois House over a bill to expand the state’s DNA database to include convicted felons. The bill, which passed easily and now goes to the Senate, would require all convicted felons to submit genetic material to the Illinois State Police.
“If we didn’t have these DNA samples, if they hadn’t saved that meal, we certainly wouldn’t be able to match it with the DNA of the people who are the supposed suspects,” said state Rep. Susana Mendoza (D-Chicago).