There are "legitimate questions" to be raised about the Toronto police investigations into the deaths of two people close to Dellen Millard that occurred before he killed Tim Bosma, the fifth estate has found.

Millard was charged with first-degree murder in the deaths of his father Wayne Millard and his ex-girlfriend Laura Babcock after he was arrested in connection with Bosma's death.

Now, questions are being raised about whether these cases could have put Millard in the sights of police before Bosma, 32, of Ancaster, Ont., was killed.

Dellen Millard is pictured in the MillardAir hangar in Waterloo. (Facebook)

"There are legitimate questions to be asked about the investigations carried out by the Toronto police in the Wayne Millard and Laura Babcock cases," Ann Brocklehurst, a journalist and author of Dark Ambition, a book about the Bosma murder, told the fifth estate

Bosma's remains were found in an incinerator on Millard's farm outside Waterloo in May 2013, days after he took two prospective buyers for a test drive in the truck he had for sale.

Those prospective buyers were Dellen Millard and Mark Smich, now both convicted of first-degree murder in Bosma's death and sentenced to life in prison with no possibility of parole for 25 years.

Laura Babcock

A year before Bosma disappeared from his property, Millard's ex-girlfriend Laura Babcock disappeared in Toronto.

Babcock was outgoing and attractive, and after she graduated from the University of Toronto, Dellen Millard entered her life.

Brocklehurst says that after Babcock met Millard, things began to spiral out of control.

"Laura Babcock was 23, she'd been dealing with mental health issues for a while and that's an age where symptoms tend to manifest themselves, so that was a bad stage of her life," she said.

In 2010, Babcock began dating Shawn Lerner — but Millard was still part of her social circle. When she disappeared, Lerner set out to try to discover why.

Laura Babcock, former girlfriend of Dellen Millard, was 23 years old when she disappeared. Millard is now charged with first-degree murder in her death. (Facebook)

A few weeks after Babcock disappeared, Lerner looked at her cellphone records and noticed something: The last eight calls she made were to Millard's cellphone.

Lerner took those call records to Toronto police, but says police did nothing. A year passed, and Babcock was still nowhere to be found.

When Dellen Millard was arrested for the murder of Bosma, Lerner wrote a letter of complaint to the Toronto police, claiming they failed to "file a missing person report … didn't collect statements from friends" and eventually "abandoned the case."

"The missing investigation was just abandoned and left open in bureaucratic limbo … and the police just gave up looking for her," Lerner wrote.

Brocklehurst told the fifth estate that as far as she knows, Toronto police have never done anything about the cellphone records.

"The Toronto police have only held one very brief press conference about the disappearance of Laura Babcock," Brocklehurst said.

"They've never given any clear answer as to whether they saw the records, or had the records, or followed the records."

Two years after she disappeared, Babcock was declared dead by police.

Stolen motorcycle

Questions have also arisen over the investigation into the theft of a trailer and motorcycle found disassembled at the MillardAir hangar at Waterloo airport.

Marty MacDougall's motorcycle and trailer were stolen shortly after he posted the motorcycle for sale online. It was found disassembled in the MillardAir hangar. (CBC)

The motorcycle had been advertised for sale online by Marty MacDougall. Not long after he placed the ad, both the motorcycle and its trailer disappeared in downtown Toronto.

MacDougall says he knew of a security camera across the street from where the motorcycle and trailer had been parked.

He told the fifth estate he called the Toronto police, who sent an officer to pick up several hours of footage. MacDougall said he didn't hear back from police, so he reached out himself.

"I emailed [the officer] about 10 times, I phoned him about 10 times, I wanted to find out myself what was on that security video and if they'd seen anything," he said. "He never responded."

After Bosma was killed, MacDougall was contacted by Hamilton police detectives who'd found the disassembled motorcycle and trailer at the hangar where Millard regularly stored vehicles.

Wayne Millard

Brocklehurst also has questions about the investigation into the death of Millard's father, Wayne Millard.

He was found dead at his home with a gunshot wound to the head on Nov. 29, 2012.

Wayne Millard, Dellen Millard's father, died from a gunshot wound to the head. His death was quickly deemed a suicide, he was cremated a week later and there was no further investigation. (Rob Seaman)

Toronto police quickly called it suicide, within a week his body was cremated and there was no further investigation.

"One question is, how was the death of Wayne Millard deemed a suicide?" Brocklehurst told the fifth estate.

Employees at MillardAir were aware of tensions between Dellen and his father.

"What I was told is that Dell's father was going to cut him off, because Dell was spending too much money and was not taking responsibility for the business and his father was not going to let him ruin the business that him and his father, Dell's grandfather, had started," Art Jennings, a MillardAir employee, told the fifth estate.

Prosecutors say that it was Dellen Millard who bought the gun that killed his father.

Several months after his father's death, and after he was arrested and charged in Bosma's killing, Millard was also charged in connection with the deaths of his father and former girlfriend.

Millard will be on trial for the first-degree murder of Babcock in September 2017, and for the first-degree murder of his father in March 2018.

Since April 2014 when they announced the murder charges against Millard for the deaths of his former girlfriend and father, Toronto police have declined to give any details about their investigations.

"Now that the cases are before the criminal courts, police will not be making statements or taking questions," Staff Insp. Greg McLane told reporters at the time.