When it rains, it pours. It's an apt motto for the Supreme Court, whose opinions lately haven't been exactly watertight.

First, there was Justice Antonin Scalia's mistaken account of a prior environmental ruling he wrote. Then there was Justice Elena Kagan's confusion over where Jews first settled in America.

And now, according to several statistics experts, it appears that Justice Samuel Alito could use some fact-checking too.

Justice Alito's forceful dissent in Tuesday's death penalty ruling contains what statistician experts say are at least two mistakes -- one of them having significant bearing on the argument that he and three other colleagues who joined him leveled against the majority.

Both apparent errors have to do with statistical tools for measuring the accuracy of an IQ test, a central issue in a ruling that gave intellectually disabled defendants greater protection from the death penalty.