DOVER, Del. — A former airman at Dover Air Force Base was sentenced Thursday to 18 months of probation in the death of a 21-month-old boy who was left in his care while his mother was deployed overseas.

Justin Corbett, who was charged with first-degree murder in the 2012 death of Evan Dudley, was convicted in July on the lesser charge of criminally negligent homicide.

Corbett, 28, maintained that the boy accidently fell down a flight of stairs after he left him alone briefly with another child.

“I will bear the burden of this tragic accident for the rest of my days,” he told Superior Court Judge Robert Young.

Prosecutor Josette Manning, who asked Young to sentence Corbett to the maximum eight years behind bars, dismissed defense arguments that Evan’s death was accidental. Manning pointed to medical experts who concluded that the boy suffered “inflicted trauma.”

“Good people do bad things, but they still should be punished for what they’ve done,” she said.

Evan’s mother, Nicole Dudley, also asked for the maximum sentence, recounting the pain she has endured and describing the many life events she will never be able to share with her son. She said Corbett not only took her son’s life, but destroyed hers as well.

“He took my life away from me,” Dudley said, recounting a Christmas Day suicide attempt in 2012. “I will never know what happiness feels like again.”

In sentencing Corbett, Superior Court Judge Robert Young noted his lack of a criminal background and exemplary military record.

The judge also noted that amount of evidence and testimony the jury considered in the emotionally charged case before deliberating over two days.

As supporters of both Corbett and Dudley looked on, some in tears, Young also noted that no sentence could undo “a terribly tragic event.”

“No one can imagine Ms. Dudley’s pain,” added the judge, who said the jury concluded that the boy’s death was neither murder, nor simply a tragic accident.

State guidelines call for a presumptive sentence of zero to two years in prison for criminally negligent homicide, with a maximum sentence of eight years.

While sentencing Corbett to the maximum term, the judge suspended the sentence for 31 days time served and probation.

Dudley expressed her disappointment as she left the courthouse.

“Just because you’re in the military doesn’t mean that you shouldn’t be held accountable for your actions,” she said. “I think the jury failed, I think the judge failed and I think justice was not served.”