The retired Prince George’s County police officer, his decorated career in law enforcement forever besmirched by a second-degree assault conviction, discussed his struggles to explain the concept of justice to his eight children. The former University of Maryland student described his mother repeatedly watching news footage of the incident, his brutal beating forever etched on her mind.

On Friday, Prince George’s County Circuit Court Judge Beverly Woodard tried to deliver justice for both men. She criticized Maryland students for the raucous celebration after a basketball game that led to John McKenna’s videotaped beating, but she turned her ire on Officer James Harrison, who struck the young man with a baton after he skipped toward a police line in March 2010. “You had a higher standard, Mr. Harrison,” the judge said.

Woodard sentenced Harrison to 30 days of home detention, followed by 18 months of supervised probation.

The sentence effectively brings to a close a case that attracted national attention after video emerged that showed Harrison and another officer, Reginald Baker, repeatedly clubbing an unarmed McKenna, then 21, with their batons.

A jury convicted Harrison of second-degree assault in October and acquitted Baker, who also had been criminally charged.

During a contentious 40-minute sentencing hearing Friday, prosecutors asked Woodard to make Harrison spend six months in jail, arguing that time behind bars for him could serve as a “deterrent” for other officers who might think of committing misdeeds.

Harrison’s defense attorney asked for the conviction to be stricken in favor of probation before judgment, arguing that Harrison’s 22-year career in law enforcement should not be erased by a seconds-long encounter that McKenna arguably instigated.

Maryland’s sentencing guidelines called for Harrison to receive anywhere from simple probation to two years in jail. The 30-day home detention sentence was effectively a compromise: It keeps the conviction on Harrison’s record but does not send him to jail.

Harrison, 48, retired from the department in November with prejudice, meaning he will be flagged if he applies for another police job in Maryland, Prince George’s County Police Chief Mark A. Magaw said.

“We respect the judge’s decision in the matter,” Magaw said of the sentence.

Baker remains on paid administrative leave while internal affairs detectives probe whether he committed any professional wrong­doing, Magaw said.

Harrison did not react audibly as the sentence was read. He had pleaded for leniency, his voice quavering, his tall frame swaying as he read from a prepared statement in which he said he felt he had been unjustly “branded a criminal.”

“I would like to state that I don’t agree with the verdict I received, but I accept it,” Harrison said.

He did not apologize for his conduct during his remarks. In the past, he has argued that his use of force was reasonable.

McKenna spoke of coming home to his mother after the incident, bloodied and trying to explain that the criminal charges initially filed against him were fabricated. Those charges were later dropped, as the video contradicted a police account of what happened.

“It has changed my life forever, and I had absolutely no say in the matter,” McKenna said in court.