With a ski mask, a fake Facebook profile and a plan, police say Kyle Dube thought he could make himself a hero.

Now the 21-year-old Maine man is set to go on trial, charged with killing a teenage girl in what authorities call a botched attempt to look like he was rescuing her from a kidnapping.

Dube's murder trial is expected to last two weeks and his defense has already received one setback: The judge will not allow his attorneys to name his ex-girlfriend as an alternative suspect in the killing of 15-year-old Nichole Cable.

Dube, of Orono, is accused of using a fake Facebook profile to set up a meeting with the Glenburn teen in May 2013 but ended up killing her in the process of a kidnapping investigators say he intended to solve himself.

Defense attorneys wanted to name Dube's former girlfriend, who was dating Dube at the time of the killing, as an alternative suspect, saying the girl disliked Cable because she believed Cable and Dube were seeing each other. But Superior Court Justice Ann Murray on Friday granted the state's motion to exclude defense attorneys from naming another possible suspect.

Murray's order said that Dube "set forth a tenuous suggestion of motive" in his call for the alternative suspect. The defense's request "does not reasonably establish any connection between" the girl and the crime, she wrote. There was also no evidence that the girl was at or near Cable's home on the night of Cable's disappearance, she wrote.

"This trial must be the trial of Kyle Dube," Murray wrote.

Defense attorneys and prosecutors declined to comment on the case until Monday's opening statements.

Cable's father, David Cable, declined to comment on the trial beyond saying, "if you're a father, you know how I'm feeling right now." Her mother, Kristine Wiley, declined to comment.

Friends and classmates of Nichole Cable at Old Town High School said after Dube's arrest that they planned to reduce or end their use of social media. Nearly two years later, the school district continues to stress the importance of using social media safely and responsibly, said David Walker, superintendent of Regional School Unit 34, which includes the high school. He said he hasn't seen a dramatic change in the way students use social media at the school.

"Hopefully they recognize that the Internet isn't always a safe place," Walker said. "Everyone is reminding students of the dangers, both parents and teachers."

Police have said Dube told other people he planned to abduct Nichole while wearing a ski mask, return later without the mask, find her and appear to be a hero. The state's chief medical examiner said Cable died as a result of asphyxiation. Her remains were found in Old Town eight days after the abduction.

Police said the fake Facebook profile was under the name of another young man but was traced back to Dube's home. That man had no involvement in the abduction, police said.