Lindsay Lohan's former assistant has reportedly agreed to give evidence against the star.

The troubled actress is facing a series of charges relating to a car accident last June - including resisting, obstruction, providing false information to a police officer and reckless driving - and her former employee Gavin Doyle has agreed to co-operate with prosecutors and confirm Lindsay was behind the wheel when the crash occurred.

A source told ''Gavin was formally subpoenaed by prosecutors last month. He was the passenger in the Porsche Lindsay was driving when the car accident happened last summer.

''Gavin has been cooperating with prosecutors and will testify that Lindsay was driving the car that day. He will tell the truth, because he has nothing to hide. He has been extremely concerned for her health and well-being.''

The 'Liz & Dick' star - who has rejected a plea deal that would see her avoid jail time in return for a 60-day stint in rehab because she doesn't have an alcohol problem - is expected to be shocked by Gavin's willingness to help prosecutors but he believes it is in his famous ex-employer's best interests as it will help her ''get her life together''.

The source added: ''Lindsay will likely be stunned at Gavin's willingness to cooperate with the case against her. Gavin just wants Lindsay to get her life together. If Lindsay doesn't reach a plea deal in the case, Gavin will testify against her, and he won't be forced to do it.''