When clams are dead they're no longer safe to eat and should be thrown out.
A good way to know if the clams are dead and no longer edible is to look for signs of gaping shells on the clams.
Gaping shells on clams indicate that the clams are no longer alive and are no longer safe to eat and have gone bad.
If the clam shell of the clams move when you touch them then the clams are still alive and are good and safe to eat.
If the clam shell doesn't move when touched then it's dead and no longer safe to eat.