OKLAHOMA CITY, Oklahoma - A former Tulsa dentist will spend the rest of his life in prison after a jury found him guilty of murdering his girlfriend's little boy.

The boy's mother spoke after Friday’s sentencing about the case for the first time.

Bert Franklin was babysitting 19-month-old Lincoln Lewis back in July of 2016 when the boy was killed.

The toddler's mother, Roxanne Randall, said Lincoln was born premature and struggled with health issues during his short life.

She said the baby was just starting to stabilize when he was killed.

Investigators said Franklin caused the head injury that led to Lincoln's death.

A judge sentenced Franklin Friday to life in prison without parole.

The baby's mother said it’s a huge weight off her shoulders to know Franklin will never be released.

"Just relieved with the verdict. With the sentence and that he will never, never be out of prison," said Randall. "I just made sure I went over everything that happened and what a threat he is to myself and my family. And the community, and babies.” 

Franklin was also found guilty of trying to hire a hitman while he was in prison to kill Randall before his trial began.

He got a life sentence on that charge. The sentences will run back-to-back.