The contract killer of Beatrice "Biddy" Gold, the London woman shot dead in the basement of her clothing business 35 years ago, might still be at large, it emerged this week.

The Criminal Cases Review Commission (CCRC) confirmed that the case of John Errol Heibner, convicted in 1976 of Mrs Gold's murder, will be referred back to the Court of Appeal.

Heibner, who was jailed for life with a minimum tariff of 25 years and was released recently, has always maintained his innocence and has received support from Lord Ramsbotham, the former Chief Inspector of Prisons, and the Reverend Nicholas Stacey, former chaplain at Maidstone Prison.

His solicitor, Rhona Friedman, who applied to the CCRC in 2002, said her client has always protested his innocence. She added that this was one of the last of the cases of alleged police corruption from the 1970s left unexamined by the courts "and represents an extraordinarily murky episode in our criminal justice system".

Mrs Gold, then 47 and a member of New London Synagogue, ran a clothing shop in Clerkenwell Road, Clerkenwell, east London, with her husband Eric.

The case may take up to a year to come to court.