age and arbitrariness

Regarding the juvenile justice resolution, one of the more intriguing Affirmative arguments I heard this weekend considered age as an arbitrary measure of competency.

The argument goes something like this:

1. Some juveniles (persons below the age of 18) are more competent (and hence culpable) than adults.

2. In the U.S. justice system, the age of majority varies from state to state, or from time to time.

3. Any brightline is a social construct, since it arises out of a political process rather than from an essential trait. (Some Affs argue further that adolescence is a social construct, which is interesting, but not necessary to make this argument.)

4. Therefore, age is an arbitrary way to determine competency and culpability.

The argument is tied to a value of justice with a criterion of "rejecting arbitrariness" (or a related phrase). At first blush, it seems powerful: arbitrariness, defined as discretion based solely on individual judgment, with connotations of caprice or despotism, is unjust.

There are at least two problems with this approach.

First, any human institution will have a degree of arbitrariness, or to phrase it more positively, discretion. Evidence and testimony, laws and statutes are open to interpretation; that's why we have juries and highly trained judges--or even panels of judges--tasked with interpreting laws. There is simply no way to entirely reject arbitrariness in the United States criminal justice system. Perhaps a more defensible criterion would be reducing arbitrariness. (As an aside, the Aff is on stronger ground to argue that the lack of a jury trial increases arbitrariness, leaving the decision in one person's hands, rather than in a unanimous verdict of strangers. But the judge is an expert, whereas the jury.... but that's another matter.)

Second, there's a deeper concern. The affirmatives who ran this argument typically promoted a test of mental competency for all defendants charged in the criminal justice system as their way to treat juveniles as adults, and overcome the arbitrary brightline of 18.

But there's a gaping hole in this approach. A measurement of competency is equally socially constructed, and more arbitrary than age.

After all, who determines the criteria of competency? Psychologists? Neurologists? Politicians? Who adjudicates the conflict between competing experts who might wish to employ different criteria? Who designs the test(s) of competency? How are the tests determined to be valid and reliable? Who administers the test(s)? Who ensures that testing bias (or interpretive bias) stays out of the process? Who ensures that test subjects aren't cleverly faking incompetence? Who draws the brightline?

And, most important, where do we draw the line? How do we know the brightline between "competent" and "not competent" is itself not completely arbitrary?

In short, a individually focused, continuum-based approach seems initially like a solid reason to affirm, but on closer inspection, produces more problems than it solves, and ultimately is self-defeating by its own logic.