At the time of the crime, there was a five year statute of limitation on murder, which had expired by the time Michael was charged. In upholding the conviction, the Court overrruled its own 1983 precedent.
Also, since Skakel was 15 at the time Martha Moxley was murdered, had he been charged in 1975 when the murder occurred, he would have been tried in juvenile court and if convicted, received a sentence of no more than two years. That's how juveniles were treated back then in Connecticut.
Skakel should never have been tried in adult court --the law in effect in 1975 precluded it--and his trial and conviction were contrary to the five year statute of limitations in effect at that time. More on that here. The 89 page opinion in January that the Court refused to rehear today is here. (pdf)
I have followed the case since the beginning since my pal Mickey Sherman defended Skakel. I was able to attend a day of the trial. Here's my take on the case and my view of what went wrong at trial.
Despite the paltry lack of credible evidence and the lack of any physical, forensic or DNA evidence linking Michael to the murder, the jury convicted. I have always thought the jury did not decide the case based on the evidence presented and refuted, but on their sympathy for Dorothy Moxley and their dislike for the well-known Skakel/Kennedy families.
[My chronology of news articles on the case from 2002 is here; 2001 is here. TalkLeft coverage is here.]