The Crown says the Christchurch man accused of murdering baby Ihaka Stokes has lied when giving evidence, the night Ihaka died and when on the stand, not to cover for Mikala Stokes but to protect himself.
Troy Taylor, 23, is accused of murdering his stepson Ihaka, and assaulting the 15-month-old on or about July 2 last year at the Bryndwr house where he lived with Ihaka's mother.
Crown prosecutor Mark Zarifeh said putting the blame on Ms Stokes is a "desperate attempt" for Taylor to get himself out of trouble.
The Crown alleges Taylor's history of concussions and headaches "helps to explain" why a "seemingly-loving, father figure" could fatally injure Ihaka.
"He snapped and inflicted those injuries on Ihaka, while Mikala was asleep in bed. When he realised Ihaka was in a very bad way, he alerted Mikala," Prosecutor Zarifeh said.
He said Taylor's recount of the events leading up to when Ihaka died was implausible, fabricated and inconsistent with medical reports of Ihaka's blunt force injuries.
Saying, 'I know what I saw that night,' doesn't explain the "complete implausibility" of Taylor's claims, the Crown claimed.
"The medical evidence not only cuts through his claims, it also shows she couldn't have done it," Prosecutor Zarifeh said.
Mikala Stokes was alone with Ihaka for several hours on the day he died in July 2015.
The Crown said a medical report showed there was a "very rapid deterioration to death" and the "pathology was not compatible with the fact the child had been in a critical state for more than four and a half hours."
"'Science can be wrong' is not an answer to the implausibility of his claims," Prosecutor Zarifeh said.
He said the factor of timing clearly shows Mikala Stokes could not have inflicted the fatal injuries.
"The only conclusion you can reach is Troy Taylor must have inflicted those injuries on Ihaka Stokes on the Friday night and it was a reckless killing…" he said, that was carried out "with murderous intent."
He said the law categorises that as murder.
Defence warns jury if they're not sure, they must give not guilty verdict
Defence lawyer Phil Shamy said police investigating Ihaka's death had decided Taylor was responsible before any pathologist or paediatric radiologist had given evidence and while there was no forensic evidence or any other evidence collected.
"The whole interview is, 'Look you didn't do it, tell us Troy did.' It's called investigative bias," he said of Ms Stoke's questioning by police.
He said police pushed Taylor to confess, but when asking Ms Stokes whether she killed Ihaka, said 'We need something more affirmative,' after she said she could have been sleepwalking and didn't know.
The Crown earlier said Ms Stokes said later, 'No…' and that she would never cause any injuries to her children to police.
Ms Stokes was heavily pregnant when Ihaka died.
Mr Shamy questioned why clothing from Ms Stokes was not sent for scientific testing, as well as why other potential evidence like clumps of white hair found in Ihaka's cot wasn't examined.
"What might have been revealed by looking at her clothing?"
Mr Shamy urged the jury to take great care when examining the case, saying the case isn't about science but a young man.
He said if jury members don't know who to believe at this point in the trial, then the verdict is 'not guilty'.
"You've got to be sure in a case like this, you can't convict Taylor by default… don't convict him by default."
Justice Cameron Mander will summarise the trial tomorrow morning, before the jury is retired to consider their verdicts.