A jury found the defendant guilty in the death of Maryland State Trooper Wesley Brown.
Cyril Cornelius Williams was convicted of first-degree murder, use of a handgun while committing a crime and possession of a handgun.
The jury heard closing arguments earlier Friday.
Prosecutors said Williams shot Trooper Brown outside an Applebee's restaurant in Forestville in June 2010.
The prosecution opened closing arguments by asking the jury, "Why are you disrespecting me? Why are you disrespecting me?"
According to prosecutors, those are the words Williams said to Trooper Brown before shooting him dead.
Brown was off-duty, working as security at the chain restaurant. Prosecutors said Williams was angry after Trooper Brown and another off-duty officer ejected him from the bar for being intoxicated. They allege that Williams got a gun from a friend, went back to the restaurant and then shot Brown dead.
Williams's attorneys argued that there is no physical evidence that places him at the scene of the crime.
A friend of Williams already pleaded guilty to helping cover up the crime by hiding the weapon used in the killing.
Before the jury returned verdicts on first-degree murder and use of a handgun while committing a crime, the defense asked the judge to rule on the handgun possession charge. Because of a prior felony conviction, Williams was not allowed to possess firearms.
Prosecutors will ask for life without parole when Williams is sentenced May 10.