Andrew Conley, 17

Andrew Conley, 17 (Photo: Courtesy Indiana State Police)

RISING SUN, Ind. -- A southern Indiana teenager who pleaded guilty to murder confided that he wanted to be just like the TV serial killer Dexter a few weeks before he strangled his 10-year-old brother, his ex-girlfriend testified Tuesday.

Alexis Murafski told a judge about her conversation with Andrew Conley shortly after the 18-year-old defendant read a statement in court in which he said he was sorry for killing his brother and didn't understand why he did so.

Defense attorneys objected to prosecutors asking Murafski about Conley's interest in the Showtime series "Dexter," but Ohio Circuit Court Judge James Humphrey allowed the testimony since Conley had told police officers he felt like the fictional character after killing his brother.

Murafski, 15, testified that Conley talked about the Dexter character while they were walking in the small Ohio River town of Rising Sun near where Conner Conley's body was later found.

She also testified that Conley had told her he had recently tried to commit suicide and had cut himself because of arguments he had had with her and his parents.

In the fifth day of the sentencing hearing, Conley was calm from his seat at the defense table as he read the statement, which took just a few minutes.

"I am very sorry for murdering my little brother and I will never forget how much he meant to me and so many other people," he said.

"I still have no idea why this happened but I really wish I did."

Two mental health experts testified Monday that Conley told them he felt as if he were watching Conner's killing while it occurred, a condition they said is known as dissociation and is brought on by stress.

Conley said in his statement that he goes to sleep every night wishing he could change what happened.

"I will accept wholeheartedly the punishment I am given and deserve," he said.

The teen faces 45 years to life in prison after unexpectedly pleading guilty last week, avoiding a jury trial.

The hearing is expected to end Tuesday afternoon, with the judge ruling on a sentence within a few weeks.

Prosecutors are seeking a sentence of life in prison without parole and are expected to argue that Conley is a psychopath who likely will kill again if he's ever released from prison.

Defense attorneys have maintained that he is seriously mentally ill.