An image made from a March 3, 2010, video taken by a student from a dorm-room window and provided by the Roberts & Wood law firm shows the incident between Prince George’s County police and University of Maryland student John McKenna. (Anonymous/AP)

Long before John McKenna enrolled at Catholic University law school, he learned how unpredictable the legal system can be.

In March 2010, McKenna, then a junior at the University of Maryland, was beaten by two Prince George’s County police officers as he headed to a bar with his friend.

One officer was acquitted and has returned to duty. Another spent 30 days in home detention for second-degree assault and 18 months on probation. It was a disappointing outcome for McKenna, who hoped for harsher punishments. But, he thought, at least he received a modicum of justice.

Now, McKenna says he has been let down by the legal system again. Earlier this month, a Prince George’s County Circuit Court judge ruled that the guilty verdict and sentence James Harrison, 50, received be stricken from his record. Judge Beverly Woodard’s decision means that as long as Harrison, who has retired from the force, keeps a clean criminal record, the case will be expunged from his files in 2017 as if he had never been found guilty of assault.

“The people of Prince George’s County should be upset about this and worry that the justice system can’t police their own cops,” said McKenna, 26, now in his second year of law school.

In March 2010, John McKenna, then a junior at the University of Maryland, was beaten by two Prince George’s County police officers as he headed to a bar with his friend. (Marvin Joseph/The Washington Post)

McKenna’s case dates back to a raucous celebration of the school’s victory over Duke in a men’s basketball game. McKenna was skipping down the street with a friend when, according to video capturing the scene, they ran into a police line and encountered an officer on horseback. As McKenna backed away from the horse, officers, including Harrison, are shown running toward McKenna and then beating him with batons.

McKenna suffered a concussion and was arrested for allegedly beating an officer. Those charges were dropped after video emerged contradicting the police account.

“The injustice is incredible,” said McKenna’s attorney, Terrell N. Roberts III. McKenna “was not only beaten, he spent the night in jail. This guy [Harrison] found guilty of assault gets no jail time . . . while his conviction is wiped away.”

Phone messages and other attempts to reach Harrison’s attorney were unsuccessful.

Prince George’s agreed to pay McKenna $2 million in a civil settlement and about $1.6 million to nine others who were falsely arrested or physically assaulted the same night. The case also spurred several changes within the police department. For example, officers deployed in the Civil Disturbance Unit now have their ID numbers prominently displayed on their helmets. And the department ordered more cameras to record events.

John Erzen, a spokesman for the Prince George’s County State’s Attorney’s Office, said prosecutors are also disappointed with the judge’s decision.

“Ultimately, we believe that these officers’ actions were criminal, which is why we took the case to trial,” Erzen said. “We believe that the jury spoke loud and clear as to the type of policing they feel is acceptable in Prince George’s County.”

Angelita Plemmer Williams, a spokeswoman for the Maryland judiciary, said it is common for judges to allow convictions to disappear from records — known as probation before judgment — if people request that they be removed and “otherwise have an unblemished record.”

Plemmer Williams said that Woodard did not overturn Harrison’s conviction but issued a “stay,” meaning that when Harrison applies for a job, the misdemeanor conviction won’t appear on his record.

Harrison’s attorney indicated to the judge that Harrison would not apply for police jobs, a condition of his departure from the Prince George’s Police Department, Plemmer Williams said.

Domenic Iamele, a Baltimore attorney who has significant experience in police use-of-force cases, said based on video footage of McKenna’s assault, it was clear the officers did not have justification to beat him up. But Iamele said it was reasonable for the judge to grant Harrison probation before judgment, especially because Harrison had served his sentence, was not convicted of a felony, left the police force and had a clean record before the conviction.

“There is no good and cogent reason to continue the punishment of this man,” Iamele said, “particularly if he has a job opportunity. Why should his record be blemished that he may not be able to get the job or keep the job?”

McKenna worries that erasing this conviction for Harrison won’t deter other officers from carefully thinking about when they use force against civilians in the future. As a law student, McKenna said there is little he can do about the judge’s decision other than to keep telling people about his experiences and use his future degree to help others.

“I was thrust into a media frenzy during my junior year of college all because I skipped down the street somewhat jovially after a basketball game,” McKenna told the judge as he asked her to deny Harrison probation before judgment. “Mr. Harrison committed a serious, violent crime against me, was found guilty of that crime by a jury of his peers, and he needs to pay for that crime.”