
A mum who murdered her five-year-old son before his body was dumped in a river has lost a bid to overturn her conviction.
Williamson denied murder and applied to the High Court for leave to appeal.
Her partner John Cole, 41, and stepson Craig Mulligan, 14, were also convicted of the murder.
Williamson’s barrister Peter Rouch told the hearing evidence relating to Cole’s previous convictions and racist past should have been admitted during the murder trial.
That evidence, which was not heard before the jury, was ruled inadmissible by the trial judge.
But three High Court judges said the initial ruling by Mrs Justice Jefford was “impeccable”, and threw out Williamson’s bid.
The Lord Chief Justice, Lord Burnett of Maldon, said the prosecution case against Williamson was that of “joint enterprise” along with Cole and Mulligan, who were also both jailed for life.

The judge said because Cole’s alleged racists beliefs, criminal convictions and history of violence were all 15 years old, the trial judge was within her rights to rule evidence of them as inadmissible.
“It follows that despite the advocacy of Mr Rouch,” he said, “this renewed application for leave to appeal against conviction must be dismissed.”