BANGOR, Maine — A Superior Court judge on Thursday denied a new trial for the teenager convicted of murdering a rival in a street fight 18 months ago.

Zachary Carr, 19, of Bangor was found guilty of murder and not guilty of manslaughter by a Penobscot County jury in March.

In addition to denying the motion for a new trial, Justice Michaela Murphy also denied a motion for acquittal on the murder charge.

Murphy tentatively set Carr’s sentencing for mid-August. He faces a minimum of 25 years and a maximum of life in prison.

Carr was convicted of intentional or knowing murder in the shooting death of John “Bobby” Surles, 19, of Bangor around 6 p.m. Jan. 27, 2010, on Cumberland Street in Bangor. Surles died the next day.

Defense attorneys F. David Walker IV of Portland and co-counsel Thomas Matzilevich of Bangor in April filed the motion seeking a new trial, which is standard in murder convictions, and a reversal of the verdict.

The motion argued that Carr’s conviction should be overturned because the state failed to prove he acted intentionally and knowingly when he shot Surles and failed to disprove that the defendant acted in self-defense, which the state had the burden to disprove, and that prosecutors violated rules of evidence.

The judge held a hearing on the motions in May but did not issue her ruling until Thursday.

Murphy said that she found that Assistant Attorney General Andrew Benson, who prosecuted the case, had not intentionally withheld information from the defense team. She also found that the receipt of new evidence had not affected Walker and Matzilevich’s ability to defend Carr since the trial was delayed twice because of discovery issues.

“There were very few choirboys in this trial,” Murphy said of the prosecution and defense witnesses. “This trial was clearly about the credibility of witnesses and it was up to the jury alone to decide the facts of the case and to decide credibility.”

Benson said outside the courthouse that he was pleased with the decision.

“The defendant was grasping at straws,” he said. “This was a frivolous argument.”

Walker expressed disappointment with the decision after it was announced and said Murphy’s ruling most likely would be appealed.

Carr’s mother, Holly Carr of Hampden, left the courthouse in tears without speaking to reporters.

Surles’ father, Allen Suddy, said at an impromptu press conference outside the courthouse that Carr had received a fair trial.

“I don’t think that my son got a fair trial,” he said.