AUBURN — A Sabattus man convicted of killing his ex-girlfriend is seeking a new trial claiming his state and federal constitutional rights were violated.

Daniel Roberts, 42, is serving a 55-year sentence in the 2005 shooting death of Melissa Mendoza, 29, of California, in his garage Aug. 15. The couple were embroiled in a custody dispute over their 2-year-old daughter, Savanna, at the time of the shooting.

Roberts failed in his 2008 direct appeal to the Maine Supreme Judicial Court, before which he alleged errors on the part of the trial judge.

In a petition filed recently in Androscoggin County Superior Court, Roberts is seeking a post-conviction review of his 2007 trial. A December hearing is scheduled. Justice Joyce Wheeler, who presided over Roberts’ trial, is expected to preside over the post-conviction review as well.

In his petition, Roberts, through his Boston attorney Rosemary Curran Scapicchio and local lawyer Verne Paradie Jr., claims his trial attorney, Leonard Sharon, and appellate lawyer Thomas Marjerison both made numerous errors in defending Roberts and deprived him of his constitutional rights.

The public was barred from parts of the questioning during jury selection, discussions of law in evidence and three conferences about possible juror prejudice, according to Roberts’ petition.

“Many individual members of the public were selectively excluded from portions of the trial,” the petition claims.

Some people complained that security officers locked doors to the courtroom during portions of the trial and locked the doors when the jury presented its verdict to the judge, according to the petition.

Moreover, court security officers refused to let members of the public into the courtroom based on their appearance. These exclusions violated Roberts’ 6th Amendment right to a public trial, the petition claims.

Roberts was not invited to participate at every stage of the trial, his petition says. Sharon, his trial attorney, failed to help Roberts secure his right to be present during all proceedings and Roberts’ appellate attorney failed to raise that failure as a point of appeal to the state’s highest court, according to the petition.

As Roberts’ trial attorney, Sharon should have sought to strike the testimony of a witness who testified in violation of an earlier court order. Or, after the witness violated the order, Sharon should have asked Justice Wheeler for a curative instruction to the jury, the petition says.

The witness testified that he felt his car tires had been slashed as a warning message from Roberts. Earlier, Wheeler had ruled that the acts of vandalism described by the witness could not be used to show Roberts’ prior bad acts during his trial, the petition says.

“Despite that the court had ruled that the evidence was not admissible as a prior bad act of Mr. Roberts, that is exactly how it was used,” the petition says. “Trial counsel did not make any effort to remedy this prejudicial testimony.”

At another point in the trial, Sharon should have testified on Roberts’ behalf to rebut statements made by the lawyer who represented Mendoza in an earlier child custody dispute. Sharon had represented Roberts during that dispute, but Sharon couldn’t take the witness stand to give Roberts’ side because Sharon was serving as Roberts’ defense lawyer.

Sharon didn’t move for a mistrial and didn’t recuse himself despite the conflict, the petition says.

Another conflict of interest on the part of Sharon was his close friendship with Roberts, the petition says.

“As with any criminal trial, the accused’s counsel assists the accused in making crucial decisions from the inception of the attorney-client relationship,” according to the petition. “However, when this advice and this decision-making are shaped by a desire to save a personal friendship, it is without doubt that the attorney’s capacity is impaired.”

Sharon should have objected to the admission of protection from abuse orders from 2003 and 2004 because they weren’t relevant and were “extremely prejudicial,” Roberts’ petition says.

“The state is not permitted to introduce evidence solely to give the jurors a better feeling about the alleged victim,” the petition says. “That’s not the issue. It’s irrelevant. The evidence should have been excluded.”

Sharon should have moved for a mistrial or sought a curative jury instruction, the petition says.

He also failed to call witnesses who would have supported Roberts’ defense by saying they had heard Mendoza wanted to kill Roberts, the petition says.

After Roberts’ conviction, Sharon failed to represent Roberts in the making of a presentencing report and should have presented mitigating factors in an effort to lessen his client’s sentence, the petition says.

In all, the petition alleges Sharon made more than a dozen errors in his defense of Roberts at trial and Marjerison made nearly two dozen errors in his appeal before the state’s high court.

All of these alleged errors denied Roberts his state and federal constitutional rights, according to the petition.