Before Oklahoma dentist, Dr. Bert Franklin was arrested and charged with the first-degree murder of 19-month-old Lincoln Lewis in July 2016, he had been dating the toddler’s mother, Roxanne Lewis-Randall, for just over a year. Dr. Franklin is accused of intentionally causing the child’s fatal injury, which the medical examiner’s report concludes was “a non-accidental blunt force trauma of the head.” Lincoln’s cause of death was a fractured skull. Franklin, who is tentatively scheduled to go to trial in September 2017 denies ever hurting the child.

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The toddler’s death came to the attention of national media after prosecutors alleged that surveillance video from his mother’s home showed the moments just prior to and following the time when Dr. Franklin is alleged to have fatally wounded the boy.

In a Dr. Phil exclusive airing Monday, Roxanne Lewis-Randall recounts how her baby boy, born three months premature, overcame a very rough start to his short life. “He spent the first two months in the NICU (Neonatal Intensive Care Unit). He had respiratory issues so we had one hospitalization a month.”

Despite his premature birth and a host of medical issues, she says, Lincoln was usually laughing and smiling. “He was the happiest.”

At the time of her son’s death, says the grieving mother, “He was finally a normal toddler. He was finally healthy, running around - and just being a normal baby.”

Roxanne says Bert Franklin often helped her care for Lincoln and never once did he make a negative comment to her about the boy. What does she claim she learned that contradicted that image after her child’s death?

This exclusive interview airs on Monday’s Dr. Phil. Click here to find out where you can watch the full episode.

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Toddler, Lincoln Lewis’ Grieving Mom Speaks Out: Why She Claims His Alleged Killer Was Jealous of the Child’s Father