The Court of Appeal has reserved judgment on an appeal by a couple jailed for a "salt overdose" killing of a three-year-old boy they had planned to adopt.
Lawyers for Ian and Angela Gay have asked the court to accept evidence that toddler Christian Blewitt could have died of natural causes as a result of a type of "salt diabetes".
But the prosecution argued on the third day of the hearing yesterday that the hypothetical evidence should be rejected because it was not new and simply revisited issues which had been dealt with at the original trial.
Ian Gay (39) and his 40-year-old wife, from Halesowen, West Midlands, were jailed 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 wealthy childless couple then lived in Bromsgrove, Worcestershire.
Former engineer Mr Gay and his wife, a #200,000-a-year insurance actuary, always insisted they loved Christian and his younger brother and sister, who had been placed with them for a trial period with a view to adoption.
Defence lawyers argued that, had the fresh evidence been available at trial, the jury's verdict could well have been different. As it was, the jurors were presented with just 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 for naughtiness.
According to a new witness, Dr Glyn Walters, the boy was not a victim of salt poisoning and could have been 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 - had so much sodium in his system.
Yesterday, Crown counsel William Davis QC reminded Lord Justice Richards, Mr Justice Penry-Davey and Judge Ann Goddard that there were other factors in the case apart from the medical evidence.
"Although it is entirely right that these people had no history of abuse and were of good character, they had been placed in an unusual situation," Mr Davis said.
"From being a childless couple, they had suddenly been put in a position where they had three children. As the trial judge said in his summing-up, the prosecution case was that their position was one of considerable stress and problems, particularly with Christian."
The judges did not set a date for delivery of their judgment.