This was the point i was trying to make in my OP. If there was overwhelming evidence that she had done this - then the likelyhood is she would have pleaded at the earliest opportunity.This is why it's so troubling they need hard forensic medical evidence. The case at the minute throws up so much doubt. If you knew it would be a shorter sentence maybe but she's going to go away for life. I couldn't say she was definitely guilty and send her to prison for the rest of her days based on the prosecutions current case.
The fact that they are running a trial, leaves it down to a jury to decide on the outcome based on the evidence put before them - whatever that might be.