Robert Slick, 35, testified that he recalled having 10 such conversations with Roger Bowling around 2004 while the pair drank beer and smoked marijuana. Slick said he and Bowling discussed how they'd "get rid of" the women in their lives.
Prosecutors claim Bowling killed Danielle Greenway, 32, and her fiancTe, Chris Hall, 42, before dismembering their bodies and dumping the remains in a canal off the Detroit River.
Assistant Wayne County medical examiner Jeffrey Jentzen testified earlier that Hall was shot six times, including twice in the head. He said Greenway had been shot once -- apparently through the mouth -- before her head, hands and legs were sawed off and dumped in the waterway.
Bowling, 39, is charged in both slayings. The hearing, which is to decide whether there is enough evidence to order Bowling to face trial, was adjourned until Aug. 29.
For a month before Hall and Greenway were killed, Bowling had been staying as a guest in the couple's Allen Park home, west of Detroit.
"He said that he'd cut (Greenway) up, put her body in a cooler with chains ... wrap it up and dump it in the water," Slick said as Bowling stared at his former housemate. Slick said Bowling was angry because Greenway was dating someone else. Greenway was not dating Hall at the time.
Hall and Greenway last were seen July 14. Authorities claim Greenway, who dated Bowling in high school, took her ex-boyfriend in as a houseguest.
Slick testified Monday that he'd heard about the deaths and told police because, "I had a conscience."
Slick said he believes Bowling used his father's boat to take the bodies to the canal, where they were dumped.
"That was the boat we used to go out on," Slick testified. "We talked about dropping bodies off in Lake Huron."
On the morning of July 17, someone spotted a torso in a canal leading from the Detroit River on the city's east side. The U.S. Coast Guard came upon the second torso in the river while investigating the initial report. Both were beheaded.
Their hands were sawed off at the wrists, their torsos at the mid-thigh area, Jentzen testified Monday in Allen Park District Court. An angler later spotted legs and a saw submerged near a seawall along the riverbank and not far from the canal.
"The cuts were very straight, uniform and clean," Jentzen said. "In my opinion, these would be consistent with some type of mechanical saw."
Both died of gunshot wounds, Jentzen said. Greenway was shot once in or through the mouth. Hall, in addition to the gunshot wounds to the head, was shot once in his spine, twice in his left side and once in his left arm.
Police believe the couple was shot at home.
Defense lawyer Mark L. Brown has said there was no eyewitness testimony linking Bowling to the killings.