Debate over cause of boy's death
Medical and legal experts were unable to agree about what caused the death of three-year-old Christian Blewitt.
The judge told the jury that the cause of death was a severe brain injury, but the jury had to decide whether he was assaulted or died from an abnormally high level of sodium in his bloodstream.
They also had to decide how that salt level came to be so high.
The prosecution claimed the boy was force-fed between two and six teaspoons of salt by the Gays, "probably as a punishment".
But the couple, who hoped to adopt Christian, produced new medical evidence which suggested he died as a result of a rare "salt diabetes" condition.
Dr Glyn Walters, a consultant chemical pathologist, told the court that Christian died from natural causes.
He said Christian's osmostat - the part of the brain that regulates sodium in the blood - may have become naturally "reset".
In evidence not heard at the first trial, he argued that, if the osmostat was reset upwards, the body would retain more sodium than normal.
He told the jury that a high level of sodium in the bloodstream was normally remedied very easily by giving the patient water.
But he added: "They (the doctors) gave Christian water and still the sodium level did not fall.
"That led me to believe that something odd was preventing his sodium level from falling.
"I have postulated that there was somewhere a resetting of the osmostat."
Under cross-examination, though, he admitted that only three other cases of osmostat resetting had been documented anywhere in the world. In each case, the patients carried on their lives normally.
The reset osmostat on its own, he said, was not enough to explain Christian's death.
William Davis QC, prosecuting, said that, as well as being force-fed salt, Christian's brain injury was also possibly caused by "some kind of impact caused by banging".
He said that bleeding around the brain was an indication of this.
He said: "Our case in a nutshell is the two of them together forced him to consume salt, probably as some kind of punishment."
He alleged that, at the same or a different time to forcing Christian to have salt, the Gays "manhandled him totally inappropriately for a three-year-old child", by shaking him or banging his head against a mattress.
He said that, while they did not intend to kill Christian, they should have realised how their actions would have harmed him.