Arntfield said the way the victims were disposed in Toronto — their transportation and concealment either through obliteration, dismemberment or burial of a body — "speaks to an offender who has been honing this for some time."
Typically, serial killers will also use their occupation as a way to acquire victims, and will use their time at work to scout locations, Arntfield said.
"One of the things I look at is the nexus between occupation and opportunity in serial murder," he said.
"These are allegations, but if proven to be true, it would appear McArthur used access to these locations and the equipment to help dispose of these victims."
But Arntfield said McArthur at 66 doesn't fit the known age demographic for serial killers. Serial murder, he said, has widely been thought to be limited to males 18 to 26 and that by 35, offenders are "aging out."
If McArthur is guilty, he either started relatively late for a serial killer, or his crimes go back several decades, he said.