A jury which convicted a couple of killing a three-year-old boy by poisoning him with salt was never given the chance to consider whether he could have died from natural causes, the Court of Appeal heard yesterday.
Jurors at the trial of Ian and Angela Gay had to grapple with a mass of contradictory medical evidence as to the cause of death of Christian Blewitt, the toddler they had planned to adopt, said Michael Mansfield QC.
They were presented with two options - either the couple murdered Christian by blunt force to the head or were guilty of manslaughter through feeding him salt as a punishment.
Mr Mansfield asked three appeal judges to hear fresh expert evidence supporting a third option - that Christian was suffering from a rare condition which allowed sodium levels to build up in the body to the point of overload.
The condition could explain why Christian - alleged to have been force-fed up to six teaspoons of salt, equivalent to a litre of sea water - was retaining sodium in his system instead of excreting it through his kidneys, which were functioning normally.
Ian Gay, 39, and his 40-year-old wife sat in the dock to hear Mr Mansfield present their appeal, expected to last three days.
The wealthy couple, from Halesowen, West Midlands, were each jailed for five years in January last year for manslaughter following a seven-week trial at Worcester Crown Court.
Christian died in hospital four days after being found unconscious in his room on December 8 2002 at a £500,000 house where the couple then lived in Bromsgrove, Worcestershire.
Former engineer Mr Gay and his wife, a £200,000-a-year insurance actuary, have always insisted they loved Christian and his younger brother and sister, who have since been successfully adopted elsewhere.
After the trial, one expert witness for the defence, Home Office pathologist Dr Peter Acland, suggested there was "significant doubt" about the guilty verdict and said he was concerned there might have been a miscarriage of justice.
Before the hearing in London, Mr Gay's mother, Jackie, said: "I saw them with the children six times and they were just loving parents and the children absolutely adored them."
Defence solicitor Bill Bache said: "The original jury was effectively told that the cause of death could either be A or B and nothing else.
"There is however C, which is a condition where the mechanisms for keeping the levels of sodium at a safe level in the body go wrong.
"The mechanism is called osmostat and scientists don't know quite why it happens but from time to time it resets, so it tells the body that higher levels of sodium are safe when in fact, of course, they are not safe.
"It is a very unusual condition indeed and many experts don't really understand it or appreciate that it can happen. It's a very obscure phenomenon.
"But I think the reason it wasn't raised at the original trial was simply because, although they had very many experts, they just didn't refer to it."
Mr Mansfield, heading a fresh legal team appointed since the trial, said the three children had been placed with the couple for a trial period because they wanted to adopt, being unable to have children of their own.
A newly-commissioned report from Dr Glyn Walters showed that the issue of "resetting of the osmostats" was a field of learning in which the experts were still at the frontiers of knowledge.
Dr Walters had concluded that "there is nothing in this case that can be explained by salt poisoning that cannot be equally well explained by resetting of the osmostats".
The trial continues.