The older half-sister of Tiffany Gayle, the Brampton teen found beaten to death in a bloody bathtub three years ago, testified Wednesday that her father asked her to change her police statement after the murder.

Tiffany's parents, father Federick, 45, and stepmother Elizabeth Gayle, 46, are accused of first-degree murder in the  slaying of the 15-year-old. Investigators believe the couple used a baseball bat and a barbecue utensil to inflict some of the fatal blows.

On Wednesday, the victim's half-sister, Samantha Gayle, told a courtroom about a talk she had with her father about a month and a half ago, before the trial began.

"He wanted me to cover for him," the 19-year-old said, describing her interpretation of the conversation.

Samantha testified that the discussion was confusing, but that her father wanted her to alter what she had told investigators earlier about why she was shipped back to Jamaica just five weeks after moving to Brampton with Tiffany and their brother. In the original statement, Samantha told police she was being sent to Jamaica because she was "disrespectful" to her parents.

'I'm not going to cover for anyone'

She testified on Wednesday that her father wanted her to retract the term "disrespectful," but that she objected to that suggestion and told her father: "My sister died, and I need to know the reason why … so I'm not going to cover for anyone."

Samantha and Tiffany had shared a close bond and were confidants, court heard.

Tiffany's body was found in a tub in the basement of her Brampton family home in June 2010. Blood was found on the parents' clothing and a shower curtain was found in the sink. There were also faint traces of blood all over the floor, leading investigators to believe Federick and Elizabeth Gayle were attempting to clean up a crime scene.

Pathologists ruled Tiffany's cause of death to be blunt-force trauma and determined that she died of shock after massive blood loss and internal bleeding.

On Tuesday, Samantha had testified that her father once beat her with a belt when she was a child in Jamaica, but that she threatened to call police if he tried to hit her after they had all moved to Canada in 2009.

The trial resumes on Friday.