It hasn't.
In fact Gareth Jenkins has said that he will allow his evidence to the enquiry to be accepted by a court ... in effect what he says at the enquiry is all he's going to say. If that is enough to convict him of perjury then fine. One of the few to show a shred of human decency. Not sure how this works legally.
He was the expert witness at early trials, although there was only one case ( Seema Misra) where he stood up in court.
This was mentioned briefly this AM ... Vennels confused by problems about expert witness. The issue of his evidence, who knew what about about it and when they new is one of the important issues. Concerns about him were raised in the "Clark advice" letter which Vennels claimed not to've seen. This was sent to PO by a barrister working for Cartwright King.
In fact everyone at PO is denying having seen this letter, including a huge number of senior lawyers. One Jainail Singh denied even when told that the IT records show that document had arrive in his email account, downloaded to the hard disk of his office computer, and printed out, all within 8 min.
Admitting to knowledge of it is a bit like playing monopoly and drawing the "go to jail, do not pass go, do not collect £200" card. Anyone at PO who knew about Jenkins lack credibility should have acted to stop the Misra trial and save her from prison.
I've been following this closely for a long time. An underlying story with a few key points has slowly emerged. The issue of the expert witness is one of the real hot potatoes that could see someone locked up for perverting the cause of justice.