Helen Doe battered her sleeping brother with an iron bar on July 5 last year but was cleared of attempted murder yesterday because she was sleepwalking

A transgender police worker who battered her sleeping brother with an iron bar was cleared of attempted murder yesterday because she was sleepwalking.

Helen Doe told police she woke up in the home she shared with her brother Kenneth, 64, with an 'overwhelming hatred' for him.

The 53-year-old, from Mitcham, south London, then hit Mr Doe three times on the head with a one-and-a-half foot long metal bar as he lay in bed on July 5 last year.

He also received a broken finger as he tried to defend himself.

Miss Doe, who has worked with the Metropolitan Police for 36 years and was taking hormone tablets at the time of the attack, was found not guilty at Kingston-upon-Thames Crown Court.

John Hilton, defending, said she was suffering 'non-insane automatism' - involuntary movements she was not responsible for.

Four expert pharmacologists agreed the drugs she was taking could have caused violent behaviour.

Paul Cavin, prosecuting, said: 'The defence will point to the conclusion Miss Doe was sleepwalking when she attacked her brother and that sleepwalking and violence was due to the drugs she was taking.'

He added: 'Fortunately he did not die or suffer long-term injury at all, brain injury, however it is the prosecution case that in striking him several times with an iron bar she intended to kill him.

'It may be that she is not strong enough, maybe he blocked or parried the blows.'

The court heard Miss Doe, who works in the uniform division of the force, dialled 999 and told the operator at around 2.50am: 'I've had an accident. I think I've killed my brother. I've hit him with an iron bar. Just now, I've been building up to it.'

When officers entered the house the defendant was in the kitchen and told them: 'It's me. I did it, he's upstairs.'

Police went upstairs to check on the brother, who told them: 'I had an argument with her earlier and I woke up and she was hitting me with an iron bar... I don't like her friends.'

He was rushed to St. George's Hospital to be treated for the three wounds, plus a fractured middle finger on his left hand.

Mr Cavin told the jury Miss Doe spoke freely in the van on the way to Sutton Police Station, confessing: 'I wanted to do it. I wanted to kill him.'

She told police she woke up in the early hours of the home (pictured) they shared with an 'overwhelming hatred' for 64 year-old Kenneth Doe

Miss Doe, who has worked with the Metropolitan Police for 36 years and was taking hormone tablets at the time of the attack, was found not guilty at Kingston-upon-Thames Crown Court (pictured)

She told police officers in an interview after the attack: 'I was in a mental state and I didn't know what I was doing. That's why I need to go to a mental place.'

'She said her friendship with her brother was not a good one and woke in the early hours with an overwhelming hatred of her brother and she makes reference to muffled voices in her head.

'She describes a history of depression for which she was taking prescribed medication. She also said she was in the process of changing gender to that of a female and was having hormone therapy.'

Doe has organised lectures for Croydon LGBT and has led the Croydon Trans Group. She has been living as a woman since 2012.