A British court has reduced seven murder convictions to manslaughter in the case of a homeless man known as the Stockwell Strangler, authorities said.

Kenneth Erskine was sentenced in 1988 to a minimum of 40 years for killing seven elderly men and women in their homes between April and July 1986.

On Monday, the Court of Appeal in London reduced his convictions to manslaughter, citing new medical evidence that Erskine suffered from severe schizophrenia, The Times of London online reported Tuesday.

Erskine was 24 when he committed the crimes, but had a mental age of 12, the court found.

Erskine is to indefinitely remain in a locked unit within Broadmoor Hospital where he is being treated for a chronic, incurable condition that will require life-long treatment, patient advocate Edward Fitzgerald said.

"The basis on which Erskine will be released, if ever, will be that it is no longer necessary for the protection of the public," Fitzgerald said.