"'You have about as much choice in some aspects of your personality as you do in the shape of your nose or the size of your feet.' " -Weinberg, 349-50
After reviewing the existences of the "gay gene" and the genetic mutation that makes people predisposed to aggressive and impulsive tendencies, Weinberg includes this quote from Dean Hamer, the scientist who found these genes.
This in particular is very interesting to me because it technically takes some responsibility for his crimes away from Frediani. The untreated genetic mutation that failed from discouraging Frediani the same way someone without the mutation might be discouraged is a rather compelling argument supporting Frediani's innocence. Ultimately, the mutated genes did not force Frediani to do anything, nor do they absolve him from his actions as a "temporary insanity plea" would.
I wonder that if the jury had known about this gene mutation, and if it was explained to them in a similar way that the temporary insanity plea would be, would they have been more merciful. I don't believe so, especially considering the more conservative area of Del Mar that Weinberg had described, because I'd imagine that the jury would feel his actions outweigh any genetic mutations that he has.