The mother of Sarah Lawson, killed by her father in an 'act of mercy', has slammed the investigation into the case.

Karen Lawson spoke out after hearing an independent review had been delayed by several months.

Sarah, 22, who suffered from severe depression, was killed by her father James at the family home in Worthing in April 2000.

Mr Lawson gave his daughter a cocktail of drugs and smothered her with a pillow.

He walked free from court last June after a judge accepted he had killed his daughter in an act of mercy.

Mrs Lawson, who is separated from her husband but supported his actions, has always criticised the treatment her daughter received from the mental health service in Worthing.

Sarah died hours after being released from Homefield Hospital, run by Worthing Priority Care NHS Trust.

She had a history of depression and was first seen by the trust in 1997.

The review was jointly commissioned by West Sussex Health Authority and West Sussex social services shortly after Mr Lawson's court case.

The results were due to be published this month but one of the four members of the panel has stepped down due to work commitments.

A search has begun for another panellist before interviews with people involved in the case can continue and the review is now not expected to be ready until the autumn.

Mrs Lawson said: "It is getting ridiculous. They announced this review last year and still there is a long way to go.

"Surely this panel member knew what she was letting herself in for when she agreed to take part in the review.

"This is just a whitewash and a waste of time. The whole idea of having the NHS investigating the NHS is ridiculous and I can't see what purpose it will achieve."

Mrs Lawson had been told she could nominate someone to sit on the panel but when she put forward the name of a churchman she was told he would not be independent enough.

A health authority spokesman said the case was complicated and everything was being done to make sure the investigation was as thorough as possible.