TORONTO - A jury was warned about drawing murderous intent from instant messages during closing arguments Monday in the first-degree murder trial of a teen alleged to have manipulated her boyfriend into killing 14-year-old Stefanie Rengel.

The jury should also question whether the 17-year-old girl, who was 15 at the time, actually intended to have her boyfriend kill Rengel, defence lawyer Marshall Sack said.

The overall meaning of text sent through instant messaging chats and emails is "beyond diluted," Sack said. The Internet makes it difficult to convey subtle nuances and emotions, he added.

"Not everything everyone sends is an expression ... of their intentions."

Rengel was found in the snow outside her parents' home suffering from six stab wounds on New Year's Day 2008.

Prosecutors contend the girl on trial, driven by obsessive jealousy, pressured her boyfriend into killing Rengel. The pair were under 18 at the time and cannot be identified.

At trial, the Crown entered into evidence more than 30,000 pages of instant messaging transcripts between the girl and her boyfriend.

However, only "a few hundred words" relate to Rengel, Sack told the jury.

"Hair is talked about more than Stefanie," Sack said. "Videos are talked about more than Stefanie. Football is talked about more than Stefanie."

During the trial, the Crown alleged the girl pressured her boyfriend into killing Rengel by sending instant messages threatening to withhold sex.

In October 2007, the accused allegedly sent MSN messages to her boyfriend saying she wanted Rengel dead.

In a chilling exchange, the boyfriend, who once dated Rengel, writes: "What about Stef," according to transcripts filed with the court.

"Bang, bang," she responds.

He then writes: "I need a bang bang first ... I wanna bang you."

She replies: "I want her dead ... lol we've been through this ... If it takes more than a week then we're just going to be friends."

"She held sex out as the carrot for her boyfriend to fulfil her evil intentions," Crown attorney Robin Flumerfelt told jurors Monday during his closing address.

Some of the messages show the girl talked about harming Rengel as far back as May 2007 -- months before the teen's death, Flumerfelt said.

A message allegedly sent on May 22 from the 17-year-old to her boyfriend read: "I'm going to f--king stab her if I want."

The girl is not accused of actually ending Rengel's life.

Instead, prosecutors are relying on a "well-established" legal principle that counselling others to kill makes a person guilty of murder.

"In this case she was not just a counsellor, she was a driving force," Flumerfelt said.

"She was both the driving force and the mastermind behind the murder. And she was not going to stop."

The one-time boyfriend, who was 17 at the time of the killing, also faces a charge of first-degree murder and will stand trial this fall.