A judge in a specialist court said he will take time to consider whether a woman who has learning difficulties is no longer able to consent to make love with her husband of more than 25 years.
Mr Justice Hayden has been told how a specialist has concluded the woman's mental health has reached the stage where she is no longer capable of understanding the "sexual act" or sexually transmitted disease or pregnancy.
Lawyers representing the woman want him to make a declaration saying she "lacks the capacity" to consent to sex.
But the judge said he is dealing with issues "integral to the couple's basic human rights" and said there is a "crucial social, ethical and moral principle" involved.
He said he must ensure that he does not discriminate against people with disabilities.
The judge has analysed the case at recent hearings in the Court of Protection, where issues relating to people who might lack the mental capacity to make decisions are considered, in London.
He has outlined his thinking in an interim ruling published online.
Mr Justice Hayden said the couple, who live in London, cannot be identified in media reports of the case.
The woman's husband had initially offered to give an undertaking not to have sex with her.
But the judge said evidence had to be explored in detail before decisions were made.
Mr Justice Hayden, who also oversees cases in the Family Division of the High Court, has heard submissions from lawyers representing social services bosses at Tower Hamlets Council, who have responsibility for the woman's care, and lawyers representing the woman.
Staff at the Office of the Official Solicitor, who help vulnerable people caught up in litigation, have instructed lawyers on the woman's behalf.
"This couple found themselves in a challenging situation in which their private and sexual life was being scrutinised by a variety of professionals. For entirely understandable reasons (the husband) was, in my assessment, both frightened and embarrassed when he came to court," Mr Justice Hayden said in his ruling.
Lawyers representing the woman had argued that he should apply a general test - and decide whether the woman had the capacity to consent to sex with anyone.
"The difficulty that presents in this case is that there is only one individual with whom it is really contemplated that (she) is likely to have a sexual relationship i.e. her husband of 27 years," the judge said.
"It seems entirely artificial therefore to be assessing her capacity in general terms when the reality is entirely specific.
"On the facts of the case, for example, it may be that her lack of understanding of sexually transmitted disease and pregnancy may not serve to vitiate her consent to sex with her husband."
The judge added: "These issues are integral to the couple's basic human rights. There is a crucial social, ethical and moral principle in focus. It is important that the relevant test is not framed in such a restrictive way that it serves to discriminate against those with disabilities, in particular those with low intelligence or borderline capacity."
He went on: "I am reserving my judgment in order that I can take the time to look carefully and in some detail at the case law and its applicability to the facts of this case."