When his convictions on burglary, weapons and witness tampering counts are factored in, the 65-year-old Ates won't be eligible for parole for more than 66 years.
"We feel justice was served," said Barbara Duncsak, the victim's sister-in-law. "The jurors did a wonderful job. He was guilty and he should get the maximum."
Before sentence was pronounced, the handcuffed Ates stood up and made a short statement that prompted gasps from some of the victims' supporters.
"All I can say is, I'm innocent," Ates said. "The jury got it wrong. This is a terrible miscarriage of justice."
John Duncsak, the victim's brother, said his brother had confided in him that Ates had threatened to kill him.
"I always believed this would be true," a trembling Duncsak said as his wife and mother sobbed in the gallery. "Now the evidence has proved beyond a reasonable doubt that you are guilty."
During the six-week trial, Ates' defense centered on his physical state - at the time of the crime the 5-foot-8 Ates weighed 285 pounds.
Attorney Walter Lesnevich told jurors Ates didn't have the energy to run up a staircase, accurately shoot Duncsak and leave before police arrived, then make a 21-hour drive to his mother's home in Louisiana in order to create an alibi.
Prosecutors said that the 40-year-old Duncsak, a pharmaceutical executive, and Ates' daughter, Stacey, were involved in a bitter custody dispute after their divorce and that Stacey had serious money trouble. But Lesnevich told jurors that a custody agreement had already been settled on by the time of the killing.
At trial, Ates' sister testified that she lied to authorities about when he arrived at their mother's house, per his request.
Prosecutors built the case entirely on circumstantial evidence, as no DNA linking Ates was recovered from the crime scene.
Among the evidence: a Burger King hamburger wrapper found near Duncsak's body. Duncsak was on the phone with his girlfriend moments before he was shot and asked if she had left a Whopper wrapper in the home. She said she had not.
"This investigation turned every page, looked in every corner," Assistant Bergen County Prosecutor Wayne Mello said Thursday. "All roads inexorably and ultimately led to one and only one: This man."