Ferrante, who has steadfastly denied poisoning his wife, is expected to appeal ruling

'The light of our lives has now been extinguished,' Klein's mother said in a

A former well-respected University of Pittsburgh Medical Center researcher on Wednesday was sentenced to a mandatory life term without possibility of parole in the cyanide killing of his neurologist wife.

Robert Ferrante, 66, was convicted in November of first-degree murder in the April 2013 death of 41-year-old Dr. Autumn Klein. Prosecutors said he laced her energy drink with deadly poison.

The victim's mother, Lois Klein, said in a statement read in court during sentencing by an assistant prosecutor that the murder had robbed her and her husband of their only child.

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Locked away: Dr Robert Ferrante, 66, on Wednesday was sentenced to a mandatory life term without possibility of parole in the cyanide killing of his neurologist wife

Guilty: Ferrante (left) was convicted in November of first-degree murder in the April 2013 death of 41-year-old Dr. Autumn Klein (right)

She said, 'The light of our lives has now been extinguished.'

The statement went on to say: 'I certainly don't want to give him any credit but he has certainly ruined our lives. All she ever wanted to do was to be able to help people. People all over the world are now losers.'

The station WPXI reported Lois Klein and her husband, William, are now caring for their 8-year-old granddaughter, Cianna, in Maryland.

Ferrante, who has steadfastly denied poisoning his wife, is expected to file an appeal asking for a new trial. He declined an opportunity to speak in court after learning his fate.

Heartbroken: Klein's mother, Lois (pictured in court February 4) said in a statement read during sentencing the murder had robbed her and her husband of their only child

Claims of innocence: Ferrante has steadfastly denied poisoning Klein and disputed whether that cyanide caused her death at all

On November 7, 2013, it took jurors 15 hours of deliberations spread over the course of two days to find the medical researcher guilty of first-degree murder.

Klein and Ferrante's 8-year-old daughter is now being raised by her maternal grandparents

Allegheny County prosecutors successfully argued during Ferrante's high-profile trial that he deliberately laced his wife's creatine energy drink with cyanide he bought through his lab using a university-issued charge card two days before she fell suddenly ill in late April 2013.

Dr Klein died three days later at University of Pittsburg Medical Center, despite doctors' efforts to save her.

His lawyers made the case that she might not have been poisoned at all, citing three defense experts who said that couldn't be conclusively proved.

Ferrante said the cyanide he bought was for stem cell experiments he was conducting on Lou Gehrig's disease, because the toxin can be used to kill of neurological cells and thus simulate the disease in the lab.

But prosecutors said Ferrante was a "master manipulator" who concocted the plan to kill his wife after she pressured him to have a second child and because he may have feared she was having an affair or planned to divorce him.