A new technique in law enforcement -- called forensic computer science -- helps put a murderer behind bars.

Each morning, before she left for work, Dorothy Boyer made herself a fresh cup of hot coffee. She'd pull the coffee can from the shelf, measure its contents into a filter, and wait for the water to seep through.

But one day she began to feel ill. The following day, she was so sick she couldn't get out of bed. Her entire body ached, she had intense stomach pain and was vomiting.

The next morning, Boyer felt much better and returned to her normal routine. She got up early, prepared for her day, made her coffee and went to work. But by noon she was once again doubled over with stomach pain.

When she returned home that afternoon she noticed something strange -- the coffee can was not where she left it that morning. The next day she felt better again, and once more returned to her daily routine. But this time, before she left, she noted the exact position of the coffee can. Sure enough, when she returned from work, it had moved.

Boyer called the police, who confiscated the can and checked it for fingerprints. They found some -- her ex-husband's -- all over the can. Police arrested Richard K. Overton, who confessed he had been poisoning her coffee with a heavy metal called selenium to get revenge after she was awarded the house in their divorce settlement. Overton would have gone to jail, but Boyer refused to testify against him and, consequently, he went free.

But as it turned out, the poisoning was just one step in a trail of lies and deceit that would eventually lead to the murder of Overton's third wife, a crime from which he again almost walked away free. Ironically, just as Overton hid poison in an innocent-appearing can of coffee, the evidence that would convict him -- remnants of his personal diary -- resided in a seemingly empty computer disk.

A TANGLED WEB

In January 1988, Overton's third wife, Janet, suddenly collapsed and died in the driveway of the couple's home. Investigators were unable to determine a cause of death.

Boyer read the obituary in the newspaper and decided it was time she spoke up. She called the police and told them Overton had tried to poison her 15 years earlier. By that time the remains of Janet Overton had been cremated. But police ordered an analysis of her ashes, which confirmed the first wife's hunch -- traces of cyanide.

Overton, who was by this time a professor at the University of Southern California, was arrested and charged with murdering his third wife, a trustee of the Capistrano School District. The case was handled by the Orange County, Calif., District Attorney's Office, and became one of the county's most famous and twisted murder cases.

Although they had been divorced for almost 15 years, Boyer's testimony revealed the whole scheme that led up to her coffee-can poisoning. At that time, the defendant worked for an aerospace contractor and had a top-secret-level clearance. While married, he met and married another woman -- Karoline Wallace -- adopting the identity of a co-worker to legally marry the second woman. He would tell one wife he was on a business trip while he lived with the other wife. Every few weeks, one would drop him off at the airport as if he was leaving, and the other would pick him up as if he was returning. For a year and a half, his scam worked.

Then one day Wallace needed to get in touch with her husband. She called his employer and spoke to the person whose identity her husband had adopted. He had no knowledge of her and