More on this later, but there are two revolutions in criminal justice that are quietly underway.

The first concerns the penal system, and involves the relative cost-benefit of strapping GPS monitors on convicted felons rather than imprisoning them.

However, as William Saletan notes today, the rationale behind using GPS monitors makes it difficult to restrict them for use with convicts alone:

As GPS gets cheaper, politicians will be tempted to order it not just for people who would otherwise be jailed, but for those who wouldn't. Some jurisdictions authorize it for all sex offenders, including teenage boys with underage girlfriends. Others are extending it to abusive husbands, stalkers, and gang members who might intimidate witnesses. Others are using it to enforce curfews on wayward juveniles. In Britain, some auto insurers use it to monitor drivers.

Further, since GPS monitors can still be cut off, the next step will likely be GPS implants:

And just this morning, police in Florida had to hunt down a sexual predator the old-fashioned way after he cut off his ankle bracelet. If anklets can't track sex offenders reliably, the next step may be GPS implants. Just you watch.

Scary stuff, that. Makes you wonder whether the tooth-excision scene in Twelve Monkeys will soon be playing itself out in reality as well.

Meanwhile, the second revolution has to do with determinations of culpability. There's no actual trial evidence of this yet that I know of, but with the advent of fMRI, you're likely to see defendents receiving brain scans in the future. The idea behind it will be to distinguish historical and ethical culpability; whether an individual actually killed someone is a much different matter from whether they chose to do so or were biologically compelled to. At present we make this distinction only in cases of insanity, but as the precision of fMRI imaging increases we're likely to see it applied to a host of other disorders as well.

Like I said, I'll probably get into each of these topics in more depth later. But for now it's certainly something to keep an eye on.