PORTLAND, Maine — The Maine Supreme Judicial Court next week will hear oral arguments in the appeals of three convicted killers in two murder cases.

Darlene George, 46, of Old Orchard Beach, and her brother, Jeffrey Williams, 48, of West Hempstead, N.Y., are serving 40 years and life in prison, respectively, for murdering her husband on June 20, 2008, in the couple’s Old Orchard Beach home.

William Hanaman, 53, of Portland is serving a 40-year-sentence for killing his girlfriend, 47-year-old Marion Shea, on Nov. 11, 2009, in his Ocean Avenue apartment.

The justices will hear oral arguments in both cases Thursday, Feb. 16, at the Cumberland County Courthouse in Portland.

George and Williams were convicted in June 2010 by a York County jury and sentenced the following October by Superior Court Justice G. Arthur Brennan. The brother and sister were found guilty of murder and conspiracy to commit murder.

The key witness who testified against them was George’s longtime lover Richard “Rennie” Cassimy, 50, of Brooklyn, N.Y. He is serving eight years in prison a part of a plea agreement with the Maine Attorney General’s Office. He said that George recruited him and Williams to murder her husband and make it look like a home invasion and robbery.

Winston George, 44, was found hog-tied in the basement of the house, strangled with a rope and suffocated with a plastic bag with a rum bottle shoved in his throat, according to previously published accounts. The scheme to kill him and make it look like part of a home invasion gone wrong was hatched because Darlene George feared her husband was going to divorce her, according to court documents. The couple owned property in Old Orchard Beach, Brooklyn, N.Y., Trinidad and Tobago. She also expected to be the beneficiary of a $70,000 life insurance policy.

Williams took the stand in his own defense and denied killing his brother-in-law and being part of the plot to kill him. His sister did not testify in her own defense.

Attorneys for Darlene George and Williams are expected to argue, among other things, next week that Cassimy’s testimony was so contradictory and improbable that it was insufficient to support the guilty verdict, that testimony about Cassimy’s criminal history should have been admitted and that the trial of the brother and sister should have been held separately.

Joel C. Vincent of Portland, who defended Williams during the trial, also is handling his appeal. Stuart W. Tisdale Jr. of Portland is handling George’s appeal.

Assistant Attorney General Donald Macomber disagreed in brief to the justices. He said that judges have great discretion in deciding whether to try defendants together or separately. Quoting a previous decision, he also said that “joint trials are favored in order to conserve judicial resources.”

In addition, the prosecutor is expected to argue that cellphone records, sightings of Cassimy and Williams in Old Orchard Beach the day of and the morning after the murder, videotape showing them at a Portland bus station and other evidence was enough for a jury to conclude beyond a reasonable doubt that the two were guilty.

As for Cassimy’s criminal background, Macomber said in his brief that Brennan correctly concluded that information about the witness being charged with but not convicted of crimes in the 1990s in Trinidad should not be heard by jurors.

Hanaman was convicted in December 2010 of stabbing Shea, his on-again, off-again girlfriend, to death after the two argued over her use of prescription drugs, according to previously published reports. When Portland police broke into the apartment at the request of Hanaman’s sister, they found Shea dead on the bedroom floor with eight stab wounds.

A barely conscious Hanaman was lying beside her. He had left a suicide note in the kitchen, then washed down prescription painkillers with alcohol.

Hanaman testified at his trial that he remembered fighting with Shea over the pills and seeing a “shiny object” above her head, then, blacked out. He told jurors the next thing he remembered was being in his truck in a grocery store parking lot, his clothes covered in blood. Hanaman testified that he returned home, found Shea’s body and assumed he must have stabbed her.

Robert A. Levine, Hanaman’s Portland attorney, is expected to argue next week that Superior Court Justice Thomas Warren, who presided over the trial in December 2010, should have instructed the jury on the affirmative defense of adequate provocation manslaughter.

“The evidence did not generate such an instruction because Hanaman did not testify that he intentionally stabbed Marion Shea to death because he was angry or fearful due to provocative conduct on her part,” Macomber said in his brief.

The judge’s instructions on self-defense and the state’s burden to disprove it beyond a reasonable doubt was sufficient, he said.

There is no timetable under which the court must issue its decision.