Lawyers representing a couple accused of murdering a boy they wanted to adopt say evidence against them is weak and the claims are no more than "a theory".
Christian Blewitt died in hospital in Birmingham
Ian and Angela Gay, of Halesowen, are accused of poisoning three-year-old Christian Blewitt with salt and causing a head injury from which he died.
The couple deny murder or manslaughter and one count of child cruelty.
Roger Smith QC told Worcester Crown Court there was no evidence they held the child's head while feeding him salt.
Referring to prosecutor Julia Macur QC, Mr Smith, who is representing Mr Gay, told the jury that it was a "figment of Miss Macur's imagination".
"It is a theory and no more than that," he added.
Ms Macur had previously told the court that Christian was admitted to Russells Hall Hospital in Dudley, just weeks after the boy was placed with the couple, suffering salt poisoning and head injuries.
He was transferred to Birmingham Children's Hospital where he died, in December 2002.
Christopher Hotten QC, defending Mrs Gay, from Lutley Lane, Hayley Green, said the medical evidence was in dispute.
He said Christian's condition on admission to Russells Hall Hospital appeared "unique" and had taken experts to the limits of medical knowledge.
Mr Hotten said several medical questions remained unanswered and that at least one expert felt it was not safe to conclude that the high sodium level in the boy's blood was caused by him having ingested salt.
The barrister said one expert speculated that Christian might have been suffering from a new disease and warned the court that the cause of the child's condition may never be known.
Summing up at the end of the seven-week case, Mr Hotten reminded the panel of the now-discredited paediatrician Professor Sir Roy Meadows.
He said Prof Meadows had been impressive in the witness box with "bedside manner in spades" but had been wrong in the evidence he gave.
Christian was placed with the couple, together with his younger brother and sister, at the couple's former home in Bromsgrove, Worcestershire, after their birth mother was deemed unfit to care for them.
Mr Hotten said the couple were found suitable to adopt three children after undergoing eight months of scrutiny by Sandwell social services.
The case continues.