A couple convicted of killing their foster child by poisoning him with salt could have been wrongly convicted, according to a Home Office pathologist.
Christian Blewitt was placed with the couple in 2002
Dr Peter Acland carried out the post-mortem tests on three-year-old Christian Blewitt, after he died in hospital in Birmingham in 2002.
Ian and Angela Gay, both 37 and from Bromsgrove, Worcestershire, were convicted of manslaughter last month.
Dr Acland said there was "significant doubt" the couple had killed the boy.
The Gays were said to have force-fed the youngster four teaspoons of salt as a punishment at their then home in Bromsgrove.
The case, which ended with the couple being jailed for five years at Worcester Crown Court, heard from a number of expert medical witnesses, including Dr Acland.
Dr Acland said: "It's certainly one of the options of this case that they did indeed kill this child with salt.
"But as far as I am concerned, I am not satisfied that I can be sure that they did and I think, certainly on the medical evidence, there is significant doubt."
Mr and Mrs Gay's family are mounting an appeal against the couple's conviction and are currently examining the evidence from the seven-week trial.
Ian and Angela Gay are each serving a five-year jail sentence
Angela Gay has denied her guilt by letter from prison, writing: "It sickened me that anyone could think us capable of harming our own little boy."
Her brother, Carl Swain, welcomed Dr Acland's views.
He said: "I feel more confident now that there was definitely an underlying illness with Christian and a lot of it also points to failure to thrive and developmental delay which were signals early in Christian's life."
Christian was taken to Russells Hall Hospital in Dudley on 8 December 2002, after being found unconscious in his room.
Tests found he had excessive levels of sodium in his blood and CT scans established he had suffered brain damage.