Mohamed Karim was silent in the courtroom as a judge read the verdict on Thursday.
Jack Beauchamp, president of Morbank Financial, was found dead inside a downtown Calgary office tower in January 2006. Court heard Beauchamp was shot six times by Karim after a multimillion-dollar property deal fell through.
The justice noted that the pre-meditated nature of the crime put Karim at the high end of the parole scale.
"She more or less based it on all the aggravating factors with the planning and deliberation," Karim's lawyer, Adriano Lovinelli, said outside court.
"Although it wasn't enough for a conviction of first-degree, it led to a higher moral blameworthiness of Mr. Karim and set the (parole) term at 18 years."
Lovinelli said he and his client understood the reasons for the judge's decision.
The defence lawyer pointed out that Karim had already apologized to Beauchamp's relatives, although he didn't do so in court.
"He wanted to actually apologize on the record to the families. The families received their letters of apology and they didn't want to hear a verbal apology in court."
Robert Deer, a second man involved in the shooting, was convicted of manslaughter and was sentenced in 2012 to 16 years in prison.
Deer and Karim were initially convicted of first-degree murder, but were granted a new trial when a court ruled the original trial judge erred.
At the second trial, court heard that Beauchamp had called police for help a month before he was killed. On an audio recording from December 2005, the businessman told police he had been receiving threatening emails.
Beauchamp told the operator one email said: "If you live like a gangster, you'll die like a gangster.''
The operator told Beauchamp the emails didn't seem illegal.
Beauchamp ended the call saying: "Hopefully nothing comes of this.''
The second trial ended with the judge convicting the accused on lesser charges, ruling that Karim did not intend to kill Beauchamp and that Deer only assisted with the plan.
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