The defence lawyer for an accused teen on trial for the murder of Stefanie Rengel is arguing that apparently damning evidence from instant messages involving his client is merely 21st century adolescent banter.

Marshall Sack argued before the jury on Tuesday that in these exchanges, murder is discussed in the same breath as Halloween costumes, birthday parties and football practices.

He had previously argued that her use of LOL -- slang for Laugh Out Loud -- indicated his client was joking in her murderous talk about Rengel.

Over a period of about seven months, defendant M.T. repeatedly told her boyfriend D.B. that she wanted Rengel, someone she had never actually met, dead.

Sack argued that M.T. -- who didn't take the stand to testify -- wasn't being literal. She merely wanted Rengel out of the way so she wouldn't interfere with her relationship with D.B., CTV Toronto's Chris Eby reported.

M.T.'s boyfriend is accused of stabbing Rengel to death near her East York home on New Year's Day 2008. He will face trial for first-degree murder in October.

M.T. is accused of inciting him to commit the act.

Sack's final address to the jury began Monday and wrapped up this afternoon. Justice Ian Nordheimer will then instruct the jury in the applicable law on Wednesday morning, a process known as charging. The next step is the process is deliberations and a verdict.

M.T. is being tried as a young offender, and under the provisions of the Youth Criminal Justice Act, neither she nor D.B. can be fully named.

In his closing argument on Monday, Crown prosecutor Robin Flumerfelt told the jury that M.T. was the driving force in Rengel's "execution."

He noted that M.T. had repeatedly told D.B. they wouldn't have sexual relations together until Rengel was dead.

The night Rengel died, M.T. and D.B. slept together, according to a Facebook exchange brought into evidence. M.T. had invited D.B. to her home after the incident.

"D.B. had the knife in his hand, but M.T. had murder in her heart," Flumerfelt said.

The court also heard evidence over the course of the trial that M.T. had called Rengel's cellphone about 12 minutes after a passerby had called 911 to say he had found the mortally wounded Rengel staggering and bleeding.

In a videotaped interview conducted about 12 hours after the murder, a detective asked M.T. why she didn't call 911 or tell her parents about what D.B. had done. "I don't know," M.T. said.

With a report from CTV Toronto's Chris Eby