A father accused of punching his baby son to death has a mental age of eight, a court heard.

Paul Oldacre, 27, of Penhill, denies murdering seven-month-old Jamie on September 20 last year.

Bristol Crown Court heard he has an IQ of 70 the average is 100.

At an earlier hearing Oldacre, of Burbage Road, admitted man-slaughter on the grounds of diminished responsibility and a lack of relevant intent.

However, the Crown has rejected this plea.

Asked by defence counsel Martin Meeke about Oldacre's mental age, psychiatrist Matthew Gallwey said: "In terms purely of mental function, the ability to do arithmetic, to read and write, we are talking about children aged six, seven and eight."

Earlier, pathologist Doctor Hugh White said he found more than 20 bruises on Jamie's chest, abdomen, legs and face.

Asked by prosecutor Roderick Denyer QC what had been the cause of death, he replied that the child had bled to death internally due to a ruptured liver.

Referring to his post mortem report, the doctor said: "On the front of the left lobe of the liver there was a split in the tissue approximately four centimetres in length.

"Behind the left lobe at the back there were two splits in the tissue approximately two centimetres long and half centimetres apart.

"One of these had a maximum depth of one and a half centimetres.

"All these injuries were caused by a number of blunt impacts to the front of the chest and abdomen; the pattern would be consistent with a series of blows with a clenched fist."

He added that he had discovered a fifth of a litre of blood in Jamie's abdominal cavity, and had found other injuries including three broken ribs.

However, the baby showed no signs of previous ill-treatment and was clean.

The court had previously heard that on the morning of September 20 Oldacre's wife Sharon went to work, leaving him with their two children.

At about 4.30pm that afternoon Oldacre telephoned his wife saying he had accidentally sat on Jamie and that the baby had turned a funny colour.

Jamie was taken to Princess Margaret Hospital after Mrs Oldacre returned to their home with her supervisor, a first-aider, but he was pronounced dead at 6.33pm.

Another psychiatrist, Doctor David Reeves, told the court that Oldacre's low intelligence, coupled with his inability to handle stress, had led to an "explosion".

He added: "Very often, inadequate people are affronted by the child not co-operating.

"It is another blow to their self esteem and very often that can be the trigger to the explosion."

The judge, Mr Justice Butterfield, was today expected to conclude his summing-up to the jury and send them to consider their verdict.