The Gene Sifters

Never mind fingerprints--state law-enforcement officials want blood

[Editor's note: A correction ran concerning this story; see end of article.]

In a windowless room on the third floor at the Bureau of Criminal Apprehension (BCA) that used to be home to the departmental copy machine, a portable air conditioner shoots out a concentrated stream of frigid air. Not a bad place to be on a hot summer day, explains Terry Laber--at least not until the two new DNA sequencers are turned on, making the room uncomfortably hot. "We've tried to add ventilation," Laber says as he points to the makeshift tube that connects one of the large, white metal boxes to the ceiling, "But it still gets good and hot in here."

As Laber, assistant director of the BCA's forensic laboratory, points out various pieces of equipment recently purchased with nearly half a million dollars in state and federal funds, three forensic scientists traipse about the space, carefully avoiding collisions as they move trays of test tubes from one countertop to the other. Those tubes contain the processed blood of sex offenders--samples the state has collected from offenders convicted of felony sexual assault since 1990. They are about to be fed into the new machines, which will examine the genetic material found in the blood and decode its unique patterns with a laser beam. The result--a set of 26 digits often referred to as a "genetic fingerprint"--will be stored on the hard drive of the Macintosh computer sitting between the two machines.

With brand-new equipment in place, state forensic lab director Terry Laber says he can handle all the DNA police and politicians send his way
Craig Lassig
With brand-new equipment in place, state forensic lab director Terry Laber says he can handle all the DNA police and politicians send his way

The principle of DNA sequencing isn't new. But the speed with which the new machines can process samples, Laber says, represents a quantum leap for the lab's capability--a leap that, this spring, prompted the state legislature to drastically expand the number of offenders whose DNA will be entered into the database. Under a measure scheduled to take effect next summer, the state will process DNA not just from sex offenders, but from people convicted of crimes such as murder, manslaughter, assault, robbery, kidnapping, burglary, and indecent exposure. "We're taking a very proactive stance," says the bill's author, Rep. Doug Fuller (R-Bemidji). "These are serious criminals who aren't just committing a single crime."

In fact, felons must commit more than one offense for the database to work. When Laber's staffers receive genetic material from a crime scene, they compare its "fingerprint" to those they already have in the computer. If there's a match, police can make an arrest even if the repeat offender was not a suspect before--an event the BCA refers to as a "cold hit." The database can also eliminate potential suspects from an investigation: If, say, a previously convicted sex offender's DNA does not match the evidence found at a new crime scene, that person will be ruled out as a suspect, since the odds of one individual's DNA matching another's are extremely low. "Instead of making up some number like 'one in kajillion,'" he says, "we usually tell the press the odds are about one in a billion. But the actual odds are almost zero." (In mathematical terms, those odds are, on average, one in 1023--a 1 with 23 zeros behind it.)

Right now the state's database contains DNA "profiles" of about 10,000 sex offenders--just about right, Laber explains, since with the old equipment his staff was able to process only about 1,000 samples each year. With the new machines, it will take but a month for the same staff to add the 4,000 samples expected to start rolling in each year once Fuller's law takes effect next summer. "You take what's going on in Waseca right now," the state representative says, referring to the investigation of the murder of 12-year-old Cally Jo Larson this April. "If we currently had the database that we'll have in two years, this case may very well have been solved by now."

The database expansion continues Minnesota's tradition of staying on the forefront of forensic DNA technologies. In 1991, a year after Minnesota became one of the first states to establish a DNA database, the BCA linked Martin Perez--whose genetic fingerprint was on file because of a rape conviction earlier that year--to the rape and murder of Lowry Hill resident Jean Broderick. Perez became the first person in the United States to be arrested and brought to trial based on DNA evidence.

Minnesota was also one of seven "flagship" states that worked with the FBI to create a national DNA database, called the Combined DNA Information System (CODIS), in 1993. In 1997 Wisconsin authorities, who did not have the capabilities to analyze DNA evidence, asked the Minnesota BCA to process a sample obtained during an investigation. The sample matched the DNA of a sex offender registered in Illinois, and Minnesota became the first state to score a "cold hit" on the national system.

"We've had about 20 cold hits," Laber notes as he leafs through the file that serves as a BCA trophy case; once the new database gets up and running, he adds, that number should increase dramatically. In addition to processing samples faster, the new DNA sequencers use a new technique called Polymerase Chain Reaction (PCR), which "amplifies," or clones, a piece of DNA millions of times. So while the current database requires that the evidence taken from a crime scene, such as a semen stain, be about the size of a dime, the new database works with cellular material about one-hundredth that size.

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