In 2004, the AMA wrote an amicus brief in which they claimed that adolescents, even those that are 16 or 17 should not be eligible for the death penalty because their brains are not as developed as an adult's brain:
The adolescent’s mind works differently from ours.The AMA notes that parents know that adolescents do have the decision making capacity as adults do and therefore are unable to make an informed decision. For that reason, the AMA believes that a 17 year old who decides to kidnap their neighbor and brutally torture and kill them should be immune to capital punishment.
Parents know it. This Court has said it. Legislatures have
presumed it for decades or more. And now, new scientific
evidence sheds light on the differences.
Scientists have documented the differences along several
dimensions. Adolescents as a group, even at the age of 16 or
17, are more impulsive than adults. They underestimate risks
and overvalue short-term benefits. They are more susceptible
to stress, more emotionally volatile, and less capable of
controlling their emotions than adults.
In short, the average adolescent cannot be expected to
act with the same control or foresight as a mature adult.
Behavioral scientists have observed these differences for
some time. Only recently, however, have studies yielded
evidence of concrete differences that are anatomically based.
Cutting-edge brain imaging technology reveals that regions
of the adolescent brain do not reach a fully mature state until
after the age of 18. These regions are precisely those
associated with impulse control, regulation of emotions, risk
assessment, and moral reasoning. Critical developmental
changes in these regions occur only after late adolescence. (emphasis mine)
However, there is an area in which the AMA believes a 15 year old girl not only has the capacity to make an informed decision that she can take full responsibility for, but that she also has the capacity to decide when her parents need to be informed of this decision. Of course, this is in the area of abortion. Their ethics paper on the topic is from 1993, but is still the prevailing opinion in the AMA:
Let's see if I have this correct. Because of the fact that their brain is unable to process information like an adult, and that their brain physiology makes them prone to emotional decisions without the ability for critical thinking, teens should not be held responsible for capital punishment if they murder their neighbor. However, even younger teens, who find themselves in a highly emotional, crisis state of an unintended pregnancy, have the capacity to make a decision without parental involvement that can effect them for the rest of their lives. They are the ones that should make the sober decision of involving their parents in what may the one of most important decisions they will ever make, and one that many girls before them have grown to regret.
Physicians should not feel or be compelled to require minors to involve their parents before deciding whether to undergo an abortion. The patient, even an adolescent, generally must decide whether, on balance, parental involvement is advisable. Accordingly, minors should ultimately be allowed to decide whether parental involvement is appropriate. Physicians should explain under what circumstances (eg, life-threatening emergency) the minor’s confidentiality will need to be abrogated.Physicians should try to ensure that minor patients have made an informed decision after giving careful consideration to the issues involved. They should encourage their minor patients to consult alternative sources if parents are not going to be involved in the abortion decision.
HT: I first read of the brief on capital punishment in Miriam Grossman's excellent book "You're Teaching My Child What?: A Physician Exposes the Lies of Sex Ed and How They Harm Your Child" available here.