The sister of the boy who accused Michael Jackson of child abuse admitted in front of trial jurors that she had selectively lied about details of the case.

In testimony that was frequently contradictory, the 18-year-old who had earlier offered a damaging account of her family's stay at Jackson's home, conceded during cross examination by Jackson's attorney on Friday that she did not always tell the truth.

She also told jurors that she had previously made a police report in which she accused her father of molesting, falsely imprisoning and making terrorist threats against her - similar charges to those made by her brother against Jackson.

Lawyer Thomas Mesereau cornered the woman over why she and members of her family had told social workers Jackson had never acted inappropriately with her 13-year-old brother who later accused the star of molestation.

"So you'd lie about certain things and tell the truth about certain things, depending on what you are asked, right?" Mesereau asked the woman. "Yeah," she softly replied.

The girl, along with her mother and two younger brothers also made a video for Jackson's personal cameraman in which they described him as a loving father-figure to the family and the alleged sex abuse victim.