The Supreme Judicial Court on Thursday ordered a new trial for a man convicted of gunning down a 16-year-old outside a Geneva Avenue convenience store in September, 2011, ruling he did not get adequate representation because his lawyer spent parts of the trial asleep.

The ruling on an appeal by Nyasani Watts, himself just 17 at the time of the murder, was one of two the state's highest court issued related to the case.

In the other, it concluded that it was "cruel and unusual" for Watt's accomplice, Sheldon Mattis, 18 at the time, to have been sentenced to life in prison without the possibility of parole, under a new doctrine in which the court extended its previous ban on lifetime sentences without parole for those under 18 to people as old as 20.

According to court summaries of the case, Mattis and Watt spotted two teenagers outside the store, and then Mattis handed Watt and a gun and told him to "go handle that," referring to Jaivon Blake and the other teen Blake was with. Watt rode up behind them on a bicycle and opened fire, killing Blake and wounding the other teen.

Both Mattis and Watt were convicted for first-degree murder in 2013, but Watt got a sentence of life with the possibility of parole after 15 years because he had yet to turn 18.

The justices concluded that Watt did not get a fair trial because of his lawyer's torpor.

After first trying to figure out just how much a lawyer could sleep during a trial - the court even considered lawyers who close their eyes as a tactic to signal disgust with their opposing counsel's tactics or statements - the justices concluded that Watt's lawyer simply spent too much of the time asleep and so Watt deserved a new trial:

"Based on the affidavits, multiple people had observed trial counsel sleeping during trial. The defendant asserts that trial counsel slept recurrently and during significant moments, such as jury selection and the testimony of two witnesses, possibly including Jeremiah Rodriguez, a central prosecution witness. Codefendant Mattis confirmed that the defendant's trial counsel slept repeatedly during trial, naming two specific occasions, including the testimony of an emergency medical technician and the victim's younger brother. One of the prosecutors at trial had contemporaneously discussed with a colleague and one of codefendant's counsel that trial counsel slept on several distinct occasions, including one where the prosecutor had to rouse trial counsel to review a photograph before it was shown to the testifying witness. One attorney for the codefendant confirmed that trial counsel slept at least once during testimony; the other attorney for the codefendant stated that trial counsel's eyes were closed several times throughout the trial. The defendant's mother also confirmed the repetitiveness of trial counsel's sleeping during trial."

In Mattis's case, the court concluded he does not deserve a new trial, but that he does deserve a hearing in Suffolk Superior Court at which a judge will have to determine when he might become eligible for a parole hearing, after concluding that people convicted of capital offenses through the age of 20 should never automatically be sent away for life.

The court had ruled in 2013 that such automatic life sentences were unconstitutional for people under 18, but said today that "based on precedent and contemporary standards of decency in the Commonwealth and elsewhere," people who are 19- or 20-year-old "emerging adults" deserve the same consideration, the court said.

The court had earlier denied Mattis's request for reconsideration of his sentence, but sent the case back to Suffolk Superior Court for hearings on whether the immature brains of young people meant a lifelong prison term was unfair. And, the court concluded, in agreement with a Superior Court judge that it is:

Advancements in scientific research have confirmed what many know well through experience: the brains of emerging adults are not fully mature. Specifically, the scientific record strongly supports the contention that emerging adults have the same core neurological characteristics as juveniles have. As the Superior Court judge noted, "Today, neuroscientists and behavioral psychologists know significantly more about the structure and function of the brains of [eighteen] through [twenty year olds] than they did [twenty] years ago . . . ." This is the result of years of targeted research and greater access to relatively new and sophisticated brain imaging techniques, such as structural magnetic resonance imaging (sMRI) and functional magnetic resonance imaging (fMRI). From the detailed evidence produced in the record, the judge made four core findings of fact regarding the science of emerging adult brains: emerging adults (1) have a lack of impulse control similar to sixteen and seventeen year olds in emotionally arousing situations,15 (2) are more prone to risk taking in pursuit of rewards than those under eighteen years and those over twenty-one years, (3) are more susceptible to peer influence than individuals over twenty-one years, and (4) have a greater capacity for change than older individuals due to the plasticity of their brains. The driving forces behind these behavioral differences are the anatomical and physiological differences between the brains of emerging and older adults. See Steinberg, A Social Neuroscience Perspective on Adolescent Risk-Taking. These structural and functional differences make emerging adults, like juveniles, "particularly vulnerable to risk-taking that can lead to poor outcomes."

The justices noted that the state legislature has long made 21 the cut-off for other activities, for example, being allowed into a casino. In a concurring opinion, Justice Dalila Argaez Wendlandt wrote that after reviewing, among other things, state statutes, the scientific record and common sense:

"I conclude that they confirm what any parent of adult children can tell you: a child does not go to bed on the eve of her eighteenth birthday and awaken characterized by a lessened "transient rashness, proclivity for risk, and inability to assess consequences." Miller v. Alabama, 567 U.S. 460, 472 (2012). In recognition of this indisputable fact, society does not treat the transition from childhood to adulthood as a binary act accomplished at age eighteen; becoming an adult is much more fluid, with development continuing long after a child's eighteenth birthday. In the ways that matter for the Commonwealth's harshest punishment, young adults of the ages of eighteen, nineteen, and twenty share key characteristics with their under-eighteen year old peers; they "have diminished culpability and greater prospects for reform" than older adults and "are less deserving of the most severe punishments." ... For this reason, condemning a person in the process of "growing up" to die in prison on the basis that she falls on the "wrong" side of an arbitrary line drawn at age eighteen is inconsistent with "the evolving standards of decency that mark the progress of a maturing society."