But the starting process was a declaration that the death was suspicious.
"Man's head implodes!" Sounds suspicious to me!
Here, we have a head being crushed/collapsing in synch with someone making a gesture. In order to sustain a conviction, the prosecution would have to prove to the court that such a gesture could cause death.
Yes. But, given the witnesses, and the dearth of skulls spontaneously staving themselves in without so much as contact with a solid surface, I'm not sure it'd be so hard to convince a jury.
This is not trivial- most American jurisdictions have "junk science" laws dictating a standard of proof for putting forth scientific evidence. And unless you can show some peer reviewed documentation, or current experiments that are capable of being replicated by other scientists, you simply won't be able to sustain a conviction, because your theory of the crime will not even be allowed to be presented in court.
I noted that earlier - the prosecutor will probably avoid explicitly suggesting the suspect is telekinetic. But, as an example, if the suspect was seen making gestures like he was beating someone with a baseball bat, and the victim was seen at the same time and place acting like he was being beaten with a baseball bat, I don't think the jury would be hard to convince (modulo the character of the witnesses, character of the victim and suspect, the nature of the motives, and such). I don't think the jury will care that much about not knowing the mechanism, if the correlation is strongly demonstrated.
I think the question of whether the case ever gets to trial, and whether the jury would convict, are pretty separate. I would never expect such a thing to come to trial, for the reasons you mention. But if it did, I would not be too surprised by a conviction.