Woman Was Found Mutilated in a Fla. Canal Decades Ago. Killer Was a ‘Complete Monster’ — Who Might Have Killed Others

More than 30 years after a woman’s mutilated body was found floating in a South Florida canal, investigators say they have finally identified her killer.

The Davie Police Department has announced that Donald Lawless was responsible for the 1987 murder of 28-year-old Marilyn Decker.

Lawless, an ex-convict who died in 1995, was connected to the crime through DNA evidence.

Decker’s body was discovered on Oct. 22, 1987, floating in a canal along Flamingo Road. She had been placed inside a large black industrial bag and was nude from the waist down.

Investigators determined that she had been asphyxiated and then mutilated after her death.

Davie Police cold case detective Eddy Velazquez says Lawless “was just a monster. A complete monster.”

Velazquez believes Decker was likely not his only victim.

“He was 62 years old at the time of her murder,” Velazquez says. “And to commit a murder at 62, in my opinion, it wasn’t his first and maybe not his last. Those are almost like a serial killer’s signature. They all do something that they enjoy. And [the mutilation] was done after she was killed.”

At the time she was killed, Decker had been spending time at a laundromat near U.S. Route 441.

“Unfortunately, Marilyn’s life started spiraling maybe six months prior to her death,” Velazquez explains. “She started the year of ’87 working as a vet tech in a local veterinary office. And then just unfortunately started getting into drugs and stuff like that, and just the bad crowd. And then that’s kind of where it led her.”

The case remained cold for decades until it was reopened by the Davie Police Department’s Cold Case Unit in 2021.

Hairs recovered from Decker’s shirt and a bloody towel were re-examined for DNA. “The results indicated several of the hairs shared the same male DNA,” according to a Davie Police Department press release. A genealogist then analyzed the DNA profile and identified Lawless as a potential suspect.

Detectives learned that Lawless had lived in Florida from the early 1980s through 1993 and had a lengthy criminal record going back to the 1940s, including burglaries, theft, auto theft, robbery, fraud, battery and prostitution-related offenses.

“When Marilyn was murdered, he lived a half a mile from where she would hang out,” Velazquez says.

“I do believe they knew each other to some extent, because her sister had mentioned when she went to the morgue, she had noticed that her fingernail clippings were all cut,” he adds. “Her nails were all nicely manicured. She had obviously eaten somewhere because she had a full belly. She went somewhere with somebody and obviously felt comfortable enough to go with that person. And then this happened.”

Investigators later learned that Lawless died of natural causes in Ohio in 1995 and was cremated. Police were able to locate a distant relative and obtain a DNA sample for comparison. That sample matched the DNA found at the crime scene.

The Broward County State Attorney’s Office concluded there was sufficient evidence to charge Lawless with Decker’s murder.

Velazquez suspects Lawless may be connected to at least two other murders in South Florida with similar methods, and perhaps additional killings in other states. “He wasn’t just here in Florida. He’s originally from Ohio. And then he spent time in Chicago, Pennsylvania, and I think in California,” he says.

“I think he’s definitely involved in others,” Velazquez adds. “100%. 100%.”