The Mean Girls actress has been sentenced to jail and community service for violating her probation from a 2007 DUI charge by stealing a necklace from a jewellery store in California earlier this year (11).
She entered a no contest plea to a misdemeanour theft charge on Wednesday (11May11) and was handed three years probation.
The star's previous probation report was released after the court hearing, and the documents reveal Lohan failed an alcohol test at California's Betty Ford rehab clinic in December (11) while she was undergoing three months of court-ordered treatment.
The failed test came on the night she was accused of assaulting an employee at the centre. Battery charges against the star were later dropped.
The report, obtained by ETonline.com, states, "Interviews with restaurant employees, hotel employees and nightclub employees support the statements that the defendant drank alcohol on the night of the disturbance."
The paperwork also suggests Lohan failed another test in February (11), a month after she was released from rehab and just a day before she was arraigned on a charge relating to the necklace theft.
The report adds, "Her recent positive test for alcohol use and the allegations in the (necklace theft) matter are troubling in that she continues to violate the law, despite prior grants of probation and county jail time... The probation officer believes that substance abuse is the root of the defendant's problems."
Judge Stephanie Sautner, who was overseeing the case, refused to make Lohan undergo any further treatment for her alcohol problem and instead ordered her to complete a shoplifters course and undergo psychological counselling after she completes her jail term, which begins in June (11).
Judge Sautner said, "I'm not going to order substance abuse counselling... I don't think that's the root of her problem. She's got other problems for which she self medicates."