The key witness against Michael Ball was blasted as an “immoral liar” Monday during closing arguments at Ball’s murder trial.

Ball has pleaded not guilty to first-degree murder in connection with the death of Erin Howlett, whose remains were found in the Grand River in Kitchener in July 2013.

An acquaintance of Ball’s named Daniel Warwick has testified that he helped Ball stuff Howlett’s body into a duffel bag, dump the bag in the river, and dispose of Ball’s mattress in the aftermath.

That testimony is disputed by Ball, who claims that he had nothing to do with Howlett’s death and still has the same mattress he did at that time.

Closing arguments began with defence lawyer Brennan Smart laying out his case for his client’s not being guilty.

Smart took direct aim at Warwick, noting that he didn’t disclose his alleged role in the case until at the trial’s preliminary inquiry – meaning nothing he said could be used as evidence for police to bring charges against him.

He also reminded jurors that a police officer said he acted like a “car salesman” to get Warwick to open up.

“The car the Crown and the police are trying to sell you is Danny Warwick and his lies,” Smart said.

Smart also questioned why James Baechler, who was dating Howlett around the time of her disappearance, was never considered a suspect by police, and why the scenario laid out by the Crown didn’t include a role for a friend of his named Chris Smith.

The trial has heard that Smith owned a black truck, which was essentially identical to one seen at the river around the time of Howlett’s disappearance.

Smith left the country after testifying at the preliminary inquiry, a recording of which was played for jurors in lieu of new testimony.

“Why would they conduct themselves in this manner if they were not involved?” Smart said.

The crux of Smart’s argument wasn’t about other people who knew Howlett and Ball, but about Howlett herself.

Although the Crown contends that she was strangled, Smart told jurors that there was no evidence of strangulation or any injury of any kind on her body, and forensic investigators were not able to determine how she died.

That, he said, means it is possible that Howlett died from a drug overdose.

Smart took issue with the entire police investigation into Howlett’s disappearance and death, saying investigators had “tunnel vision” and never seriously considered anyone other than Ball as being responsible for her death.

He said this was due to his client’s “stupid, petulant, bravado-laden rants” in which he talking about tying Howlett up and buying a duffel bag for her after finding sexually charged photos and messages from other men on her phone.

Those rants, he said, were known by many people before Howlett went missing.

Closing arguments continue Tuesday, with the jury expected to be charged on Wednesday.