The court of protection has ruled that a man who cannot understand the issue of consent must be allowed to pursue sexual relationships.

Mrs Justice Roberts ruled that the man, who has autism with impaired cognition and lives in a supported residential placement, has a “fundamental right to sex”.

The court considers issues relating to people who might lack the mental capacity to make decisions.

A clinical psychologist submitted a report saying that the 36-year-old man, referred to as JB, represents a “moderate risk” of sexual offending to women, particularly to those who are vulnerable, and that JB cannot understand that a woman’s consent is relevant in sexual situations, nor that attempting sex without consent is likely to be a criminal offence.

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However, the judge said that insisting that JB understands the issue of consent before being allowed to pursue sexual relationships would be discrimination because it would “impose on him a burden which a capacitous individual may not share”.

She said not having that knowledge might result in criminal prosecution but JB was “entitled to make the same mistakes which all human beings can, and do, make in the course of a lifetime”.

JB has never been charged with any criminal offence but because of his behaviour towards women he has been subject to a care plan by his local authority since 2014 which has imposed significant limitations on his freedoms.

The local authority wanted the care plan to stay in place, but Roberts said in her judgment that JB had “made it very plain that he desperately wants to find a girlfriend with whom he can develop and maintain a relationship. He is anxious to have a sexual partner and believes that the current restrictions represent an unfair and unwarranted interference in his basic rights to a private and family life.”

The judgment said that the “decision to engage in sexual relations ... is a primal expression of our humanity and existence as sexual beings. It is an essential part of our basic DNA as reproductive human beings.”

Roberts added: “Sexual relations form a fundamental aspect of our humanity, common to all regardless of whether an individual suffers from some impairment of the mind.”

In its submission to the court, the local authority said that there was concern that JB’s behaviour, if unrestrained, “might result in his exposure to the criminal justice system and risk to potentially vulnerable females”. They said that his advances to women in the past have lacked appropriate social inhibition.

In his written submission on behalf of the local authority, Mr Vikram Sachdeva QC accused the court of a “derogation of responsibility”: “If the criminal law is left to regulate such conduct, it will mean that sexual offences will be committed by incapacitated people before the law will intervene to prevent such damaging conduct by the imposition of criminal restrictions. To permit such a situation to continue would be a derogation of responsibility by the court of protection.”

Speaking after the case, Victoria Butler-Cole QC, one of Sachdeva’s colleagues at Essex Chambers, said: “The capacity test in civil law is set as low as possible so that, for example, a 70-year-old woman with dementia who sometimes can’t remember who her husband is, can’t be banned from having sex with him.

“But there is an interesting tension in these cases which has never been tested in the supreme court illustrated in this case, where JB is judged to have capacity but is nevertheless 100% at risk of being arrested for a crime if he tries to have sex with someone without their consent.”

The local authority is expected to appeal against the decision.