Sentencing has been delayed for Joshua Nisbet of Scarborough, a convicted robber who is possibly the first defendant in Maine to be stripped of his constitutional right to an attorney and ordered to represent himself in a trial.

Justice Thomas Warren, who presided over Nisbet’s trial in the Cumberland County Courthouse in Portland, allowed sentencing to be delayed until the week of May 19 to accommodate the schedules of members of Nisbet’s family who were unavailable to speak in court Wednesday.

Nisbet, 37, appeared in court for a hearing Wednesday in which the judge raised an issue that he felt could be cause for concern regarding one of the 12 jurors who delivered the guilty verdict May 1.

The court had made an effort to keep jurors from seeing that Nisbet was wearing leg shackles, to prevent them from possibly being influenced by the fact that he was in custody. Court officers hung curtains at the front of the table where Nisbet sat, and stood behind him during the trial to block jurors’ view of his feet. The jury deliberated for about an hour before delivering the verdict.

Warren said that, as he thanked the jury for its service at the end of the trial, one juror told him that Nisbet’s shackles were visible.

“I don’t see how anything that could be seen in the courtroom could be seen as juror misconduct,” Warren said.

Neither Nisbet nor the prosecutor, Assistant District Attorney Bud Ellis, voiced a complaint about Warren’s disclosure.

Nisbet remains in the Cumberland County Jail pending sentencing. He faces as much as 30 years in prison.

Warren issued an order in March that Nisbet represent himself after his most recent attorneys, Jon Gale and Neale Duffett, sought to withdraw from the case, saying in a motion that Nisbet threatened Gale while they met with him in the jail on Feb. 26.

Nisbet has no legal training and said that he did not want to represent himself at trial. He had gone through five court-appointed attorneys after his arrest on July 18, 2011, following a police standoff days after the robbery.

Each attorney sought to withdraw from the case after citing serious breakdowns in the attorney-client relationship. Nisbet said he believes that each of the lawyers had begun to work against him.

At the end of his trial, Nisbet asked Warren to sentence him immediately. Nisbet has already spent nearly three years in jail, but cannot appeal to the Maine Supreme Judicial Court until sentencing is complete.