Lloyd Welch waived his right to a speedy trial.
http://wset.com/news/local/lloyd-welch-jr-waives-right-to-speedy-trial
On one hand, he is stuck in prison for years for his Delaware crimes, so it's not like he would be in any rush to have a fast trial to get out.
On the other hand, by not insisting on a speedy trial (I hope you paid attention in American History or Government) Lloyd has more time to prepare his case or hope an elderly witness dies before trial.
If the government case was very weak, Lloyd's lawyers would likely have insisted on a speedy trial so that that government has to go to trial with the evidence it has, and not evidence the government may find in the future. In my opinion, the government is still fishing for evidence from other family members, otherwise they would not be in legal trouble.
An unrelated case from the mid 1970s is that NYC airport robbery court case, which ended in a not guilty verdict. While unrelated to Lloyd, this case, based on (alleged or recorded) admissions/braggings, which shows the difficulties of obtaining a conviction so long after the crime. Just as a Mafia member bragging something like "I helped rob that plane and never got my fair share" was not enough to convict, I can't see how Lloyd saying something like, "I killed two girls" would be enough to convict beyond a reasonable doubt without additional evidence