Brian Malley, who is 57, is charged with first-degree murder in the death of Victoria Shachtay (SHAK'-tay) in November 2011.
The package had been left on the doorstep of Shachtay's apartment in the town of Innisfail.
The caregiver narrowly missed being injured in the explosion.
She testified that she and Shachtay had been celebrating the night before because the caregiver became a permanent resident of Canada.
Shachtay, who was 23, was paralyzed after a car crash several years before and had to use an electric wheelchair to get around.
Malley, who was Shachtay's financial adviser, has pleaded not guilty to murder and to two other explosives charges.
The Crown has told the jury that Shachtay received a settlement of $575,000 after the crash that left her a quadriplegic. Prosecutor Anders Quist has said he plans to argue that Malley lost all of Shachtay's money, was going into debt by giving her money out of his own pocket and killed her to cut his losses.
Defence lawyer Bob Aloneissi has said evidence will show some of the woman's relatives had addiction problems and the real killer was someone who wanted to send a message to Shachtay or her family.
(CHUB, The Canadian Press)
Note to readers: This is a corrected story. A previous version said Shachtay had been accepted into a residential treatment program.