RED DEER, Alta. -- A jury must decide whether a financial adviser is wrongly accused of murdering his disabled client, or a calculating killer who built a bomb, disguised it as a Christmas present and left it on the doorstep of her central Alberta home.

Closing arguments were heard Monday in the trial of Brian Malley, 57, who has pleaded not guilty to first-degree murder and explosives charges.

Crown prosecutor Anders Quist alleged Malley lost all of Victoria Shachtay's money, resorted to paying her out of his own pocket and wanted the annoying woman dead to "cut his losses."

Defence lawyer Bob Aloneissi told the jury that motive doesn't make sense.

"There's an easier way to cut your losses -- you just stop paying," he said.

"Mr. Malley is being prosecuted because he cares for people, in this case, a single mom in a wheelchair."

Shachtay was paralyzed in a car crash in 2004, when she was 16 and pregnant. Court heard she received a $575,000 court settlement in 2007 and turned to Malley, a family friend, to help her invest the money. She also borrowed another $264,000 to bump up the fund.

By April 2011, it was nearly all gone.

Court heard Shachtay later phoned Malley's office and sounded surprised to learn her account had been closed.

On Nov. 25, 2011, a green-and-gold gift bag was delivered to her door in Innisfail, just south of Red Deer. Her caregiver brought the package inside and Shachtay opened it while sitting in her wheelchair at the kitchen table.

The 23-year-old was killed instantly.

Aloneissi said it takes a "particularly despicable" person to kill a disabled mother and put others in danger. Luckily, Shachtay's caregiver wasn't hurt and her daughter wasn't home at the time.

Court heard that part of Shachtay's money was lost due to drops in the market, but Malley also put some of her funds in high-risk investments.

When it was gone, he wanted to help, said Aloneissi. Shachtay's mother had secretly given Malley $15,000 to give to her daughter before she died. He then gave her nearly $30,000 of his own.

Malley made about $600,000 a year and could afford to be generous, said his lawyer.

But court also heard another description of Malley. Quist said Malley called Shachtay stubborn and lazy because she spent too much money and wouldn't get a job, and Malley once told his assistant that Malley was "a pain in the ass."

"I'm not that nice of a guy," he told police in an interview, denying he gave Shachtay money from his accounts.

Quist reminded the jury that police plucked a napkin from a garbage at a Wendy's restaurant to get Malley's DNA and, although not conclusive, it was consistent with DNA found on a piece of paper and tape in the bomb debris.

Police also traced purchases Malley made at area hardware stores and matched some of the same parts used to make the bomb.

Malley's lawyer said some of the items were used in his home renovation work. Gun powder was needed to fill shotgun shells for hunting. And he wanted tiny light bulbs to make Christmas lights from scratch.

A piece of metal pipe and an end cap were also used to cover a gas line at his mother-in-law's house. They were dug up and provided as defence evidence in court.

Quist called the pipe find "a sham" that provides Malley with another explanation in a string of coincidences. He said Malley could have bought duplicate items with cash, leaving no paper trail.

The jury is to begin deliberations Tuesday.