2. Handiest tool

3. Junky genes speak

4. Latest and greatest

You can find testable DNA just about anywhere, as shown by the red spots on the Bascom (Hall) strangler, caught in the act.

Short, ironic history
The dual utility of DNA fingerprinting for the prosecution and the defense actually surfaced at its first use in police work. In 1986, two years after the technology was invented by Alec Jeffries of Leicester University in the United Kingdom, a girl was raped and murdered several miles from Jeffries's laboratory.

A suspect confessed to the crimes, but denied a previous, similar crime. A DNA test confirmed that denial -- and when the police DNA-tested evidence from the recent murder, they discovered that the suspect's DNA was similarly absent. The suspect, once confessed but twice innocent, walked free. With both crimes now unsolved, the police found a pretext to collect blood from local men and eventually found and nailed a man whose DNA appeared at both crime scenes. "It was an extraordinarily auspicious beginning...," wrote Harlan Levy, a former New York City prosecutor. "In its first known application to a murder case, DNA testing fulfilled both its promises, clearing an innocent man and helping convict a guilty one."

DNA fingerprinting was a whole lot less decisive in the O.J. Simpson case: The ex-footballer walked on double murder charges, even though his blood was found in compromising situations. The jury decided that the DNA evidence was tainted by police misconduct. While the DNA was neither convincing nor convicting, the Simpson trial forever changed the legal treatment of DNA:

The procedures for collecting and processing DNA have been tightened. With the tests considered unassailable, proper handling of evidence is crucial.

Judges and juries know the basic science of testing -- or at least accept its scientific validity. George Gaucys, HLA/paternity laboratory manager at the American Red Cross in Madison, Wis., says, "There's less need to testify," in the 700 or so paternity cases his lab handles each year. (DNA fingerprinting is used to prove paternity so states can prod fathers to fund their children's upbringing.)

Invasion of privacy?
DNA fingerprinting and the databases needed to take maximum legal advantage of them do raise privacy and ethical concerns. Some observers fear any misuse of the FBI's national DNA database, the Combined DNA Index System (CODIS). "These are technologies in which powerful organs in society control members with less power," Philip Bereano, a director of the American Civil Liberties Union, told Time in 1999 (see "DNA Detectives" in the bibliography). "They are inherently violative of civil rights." CODIS went online in 1998, offering access to state data on DNA related to rape, murder and child abuse.

And that's fine with prosecutors, who note that given the difficulty of preventing repeat crimes by sex offenders, and the gravity of rape and murder, databases are the fastest, best protection for the public.

Beyond political and legal acceptance, the increasing use of DNA fingerprinting reflects the introduction of a faster, cheaper and better technique that can produce a conviction from a pin-head size drop of blood. In fact, even a few skin cells may do the trick. Says Laber, "We've had good luck with cigarette butts, stamps, envelopes, ski masks, even a hat band. If you lose a hat or an article of clothing, there's a reasonable chance" your skin cells may be found on it.

Can they test blood after 20 years? Yewbetcha. I seen it on TV!