LOS ANGELES (Reuters) - The physician convicted of killing Michael Jackson regrets not testifying on his own behalf while on trial last year, two defense lawyers said on Monday after visiting the jailed doctor on the third anniversary of the pop star's death.

Dr. Conrad Murray, hired as the "Thriller" singer's personal physician in 2009, began serving a four-year jail term in November after a jury found him guilty of involuntary manslaughter.

Prosecutors argued during the six-week trial that Murray was grossly negligent in administering the surgical anesthetic propofol as a sleep aid to Jackson and that the doctor failed to properly monitor Jackson on the drug.

They also presented evidence that Murray delayed in calling for emergency assistance when the singer stopped breathing the night of his death and that the doctor failed to tell arriving medical personnel he had given the performer propofol.

Defense lawyers say Murray gave Jackson a small dose of propofol to help him sleep. But they argued the singer was dependent on the drug and likely gave himself an extra, fatal dose - and swallowed a handful of sedatives - without Murray knowing.

Two of his lawyers visited Murray on Monday at the Los Angeles County jail where he is incarcerated. Attorney J. Michael Flanagan said the doctor was "adapting fairly well for a person who is serving time and who is actually innocent".

Jackson was found lifeless at his Los Angeles mansion on June 25, 2009, about three weeks before he was due to begin a series of concerts in London aimed at returning him to the limelight after the humiliation of his 2005 trial and acquittal on child molestation allegations.

Murray's attorneys denied he was guilty of criminal negligence. But the physician himself never took the witness stand in his own defense, a decision he has come to regret, according to his appellate lawyer, Valerie Wass, and Flanagan, the co-counsel for his manslaughter trial.

Flanagan told Reuters that Murray's lead trial attorney, Ed Chernoff, was adamant that Murray not take the stand. Flanagan said he strongly disagreed with Chernoff, but Murray ultimately followed Chernoff's advice and declined to testify.

"Murray now realizes that he should have testified," Flanagan said, adding that there were various nuances in the case that Murray alone, as the only person who was with Jackson in the last hours of his life, could adequately explain to the jury.

"Now he says that the biggest mistake he made in the trial of the case was not testifying," Flanagan said. "We had so many gaps in the case that needed to be filled, that could only be supplied by Dr. Murray."

If the verdict were to be reversed on grounds of an error of law by the court or over an issue of admissibility of evidence or flawed jury instructions, leading to a retrial, the defense would then seek to put Murray on the stand, Flanagan said.

Wass, who is working on an appeal for Murray, suggested that jurors might have been influenced by information they inadvertently saw about the case through social media that they were allowed access to during the trial.

"I think during the trial, it would have been difficult not to go on Twitter and see anything (about the case)," she said. Flanagan said it would have been better to sequester the jury due to the extremely high profile of the trial.

He said he expected that Murray would end up serving no more than two years of his term, and could find himself released before his appeal ran its course, under guidelines that allow for reduced time for good behavior.