Whether it was a modified ebike or an unregistered moped will be decided by the court i assume?
Not really because it's not relevant to the charges.
The most serious charge is death by careless driving, for which the prosecution has to prove only two things.
He caused the death, and his driving/riding was careless, defined as falling below the standard of a careful and competent driver, or a momentary lapse of attention.
The type of vehicle doesn't come into it, only that it must be mechanically propelled, which for this purpose includes an electric motor.
The other two charges are simply that he had no licence for that type of vehicle and that he had no insurance - again nothing to do with the legality or otherwise of the bike.
The derestricted nature of the bike has been given in evidence, or at least, opened by the prosecutor which means he has evidence of it.
Likely to be a statement from a suitably qualified electrical engineer or traffic cop, which probably won't be challenged - assuming they got to examine the bike.
He left the scene with it, so may have tried to tinker or dispose of the bike before handing himself in.
The prosecutor has also mentioned two other strands of evidence he intends to present.
Another cyclist who said the defendant barrelled past him at high speed, and CCTV showing him going at speed without pedalling.
All that is trying to prove is he was going fast, which the prosecutor hopes will convince the jury his driving was careless.