Texas Death Penalty Paradox

If you didn't think Texas was crazy already; and if you didn't think the death penalty was crazy already; just consider this mind-blowing concept:

In Texas, they determine whether a murderer should face the death penalty based on whether s/he is intellectually impaired, which is defined as an IQ of lower than 70. Texas Puts Man With 61 IQ To Death

Okay, seems sensible enough, until you consider the implications:

So they give an IQ test to a defendant and say, "If you do well on this test, we'll kill you." It's fair to say there is a heck of an incentive to do badly, and luckily enough doing badly on an IQ test is really easy. In fact, if someone facing death by virtue of a high IQ score, is so dumb as to actually score highly, then they must be just intellectually impaired as those with a low score.