I heard on the local news this morning that Texas is running a pilot program to identify sex offenders with the “highest level of deviant arousal.” The offender is connected to a bunch of physiological monitors, including one on the shaft of the penis, and his arousal level is measured as he is shown different types of images that might be sexually arousing.
The purpose:

The state says these new tests will help them weed out the low-risk sex offenders, like the 19-year-old who has sex with his 16-year-old girlfriend, from the pedophile who seeks sexual pleasure from children on the playground.
“The folks that show the highest level of deviant arousal are the ones we need to pay the most attention to and contribute the most resources to,” said Siegel.

I’m already uncomfortable with the whole idea that sex offenders cannot be rehabilitated or that they cannot control their actions.
This test, should it be adopted, raises further questions. What about ‘false positives’: men who are incorrectly identified as being aroused by ‘deviant’ images? And to me, it seems there’s a big difference between arousal and acting on that arousal.
We’re letting these people back into society but we’re trying to tell the public that they’re likely to continue their violent behavior. I’m certainly not a fan of locking someone up and throwing away the key, but isn’t one reason for incarceration to remove dangerous people from the general population? If we are so sure they’re so dangerous, why are we letting them out of prison in the first place?