Adrian Lanzara consumed a cocktail of prescription drugs that caused drowsiness before driving his ute over a median strip and ploughing head-on into another car, killing the driver.
Tracy McInnes, 38, died at the scene on North Lake Road in Bibra Lake, in Perth's south, in August 2014, and her family, including her fiance, has been waiting for more than two years for answers.
"The last two years has caused great pain and despair," the family said in a victim impact statement read by Judge Christopher Stevenson to a packed room in the WA District Court on Tuesday.
Lanzara, 43, was sentenced to three-and-a-half years in jail for dangerous driving causing death, having changed his plea to guilty on the second day of his trial.
"You were subject to a cocktail of drugs, which you had voluntarily ingested at the time of driving," Judge Stevenson said.
The court heard that a few hours before the crash, Lanzara had gone to the emergency department at St John of God Hospital in Murdoch, where he was prescribed medication after complaining of chest pains and shortness of breath.
The triage nurse testified that Lanzara was supposed to take one tablet when he got home and then continue with the dosage every six hours until the remaining five pills were consumed.
Judge Stevenson accepted the nurse and doctor had told Lanzara not to drive or operate machinery for 24 hours after taking the medication and that he had not consumed a tablet in their presence.
But Lanzara had showed a "flagrant disregard" for their "unequivocal advice", Judge Stevenson said.
Defence counsel Max Crispe said his client believed after discussions with medical staff that he could take one tablet and drive home because it took a while for the medication to kick in and he lived close by.
The court heard that after Lanzara drove home he consumed more medication.
Judge Stevenson said there were still a lot of unknowns about Lanzara's state of mind and what happened in the lead-up to the crash.
"At some point in time, you made a conscious decision to go somewhere," he said.
"You made the fatal decision to drive your vehicle. It is an act of utmost selfishness."
Judge Stevenson also commented that Lanzara did not appear to have been full and frank with a psychologist, who described Lanzara as someone who put up barriers.
Lanzara appeared agitated while giving instructions to his lawyer during proceedings and wiped away tears at one point.
He must spend at least 21 months behind bars before he can be eligible for parole and will then have his licence disqualified for three years.