DAVIE, Fla. — After nearly four decades, Davie police say new DNA testing has solved the 1987 cold case murder of 28-year-old Marilyn Decker.

Decker’s body was found mutilated and stuffed inside a large bag floating in a Davie canal near Flamingo Road. For years, investigators had few leads — until the department’s cold case unit reopened the file in 2021.

Detectives say evidence recovered from Decker’s shirt and a towel at the scene — specifically strands of hair — ultimately led them to Donald Lawless, a man with a lengthy criminal history dating back to the 1940s. Lawless died in 1995.

“We found evidence at that scene that led us to Lawless,” said a Davie detective. “He was not on our radar — not on anybody’s radar.”

Using modern forensic genealogy, investigators built a genetic profile from the hair samples and traced it through family trees. Since Lawless had been cremated, detectives obtained DNA from his living relatives to confirm the match.

Lawless’ criminal background and the manner in which Decker’s body was dumped have led detectives to believe he may be connected to similar cases in Fort Lauderdale, Hollywood, and elsewhere in Broward County.

“There’s no doubt we believe Lawless has ties to other cases,” the detective said.

Decker’s sister, Gail Demore, said the breakthrough brought both closure and anger.

“It infuriates me that my sister’s murderer, with such a long history of violent acts against innocent victims, was left unpunished,” she said.

Decker’s parents died before seeing the case solved.

Davie police say they are now working with other local and national agencies to determine whether Lawless is linked to additional unsolved murders.

Copyright 2025 by WPLG Local10.com - All rights reserved.