The medical condition said to have left a Norfolk police officer with no memory of smashing into the back of another motorist in a road crash is difficult to diagnose, an expert has said.
Roads and armed policing officer PC Karl Warren failed to stop or report the collision when he rammed a marked BMW X5 into the back of an Audi A1 driven by a woman on the A146 between Lowestoft and Beccles.
READ MORE: Hit-and-run police officer avoids charges... because he 'can't remember' crash
Criminal charges against him have been dropped, and he will not face a misconduct case, after evidence that he was suffering transient global amnesia (TGA) that he said has left him with no memory of the incident.
A rare condition, an episode of TGA leads to sudden confusion in someone who is otherwise alert. It leaves them unable to create new memories, so recollection of recent events disappears.
Dr Michael Grey, an expert in rehabilitation neuroscience at the University of East Anglia’s School of Health Science, said stress from a road collision was a possible factor, along with physical exertion.
He said: “It is a form of anterograde amnesia. There are two types of amnesia, retrograde where you cannot recall things before the event, and anterograde which means that you cannot remember anything after.
“It will last up to 24 hours but usually one to eight hours. It’s pretty rare we are talking about one in 10,000 people.”
READ MORE: Could hit-and-run police officer’s memory loss affect other cases?
TGA most often affects people in middle or older age but the underlying cause is unknown and experts do not understand the factors that contribute to it.
Criminal charges against PC Warren were discontinued after evidence from a London consultant and a medical report provided by an NHS specialist neurologist consultant.
Dr Grey said: "It is something that is well known in the legal community but the challenge is that diagnostically it is hard to test for, especially if you are doing this 24 hours after the event.
“There is some very specialist neuro-imagining that will test positive in most cases, but it is very specialised and not something one would do routinely in the NHS.
“There are a lot of lawyers out there who think you just have to claim to have experienced TGA, but it is not as easy as that.”
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here