(CBS)- It's been more than 30 years since John Hinckley pulled a gun outside the Washington Hilton and shot President Ronald Reagan and three others in broad daylight.
Even though the crime captured the world's attention (the Academy Awards postponed airing its telecast until the next night), Hinckley would perhaps become more notorious for the outcome of his trial - not guilty by reason of insanity - than for the shooting itself.
In fact, although the shooting changed Secret Service procedures and, indirectly, led to the passage of the Brady Bill, which strengthened gun laws, it's possible that Hinckley's most enduring legacy has been his impact on the so-called "insanity defense."
And now, as Hinckley's doctors petition a Washington court for his release from the mental hospital where he has lived for three decades, the case is once again a bellwether, this time for how the judicial system treats those whose criminal actions have been found to be the result of a mental illness, once that illness is under control.
After Hinckley's 1982 acquittal, appalled lawmakers went into overdrive, creating what University of Pennsylvania Law School professor Stephen Morse calls a "wave of legislative moves to change or abolish the insanity defense."
"Juries never liked" the insanity defense, says Morse, but pre-1982 the movement in the legal community had actually been a gradual expansion of the defense, which had previously been a simple question of whether the defendant knew right from wrong while committing the crime.
Before Hinckley, explains Morse, "the wave of the future" was to allow the defense to argue that if a defendant's mental illness rendered him incapable of conforming his behavior to the law, he could be found not guilty. In addition, in many jurisdictions it had up until then been the prosecution's burden to prove beyond a reasonable doubt that the defendant was sane at the time of the crime.
But as state legislatures tightened their statutes in the wake of the Hinckley verdict, that "conformity" defense was abolished in some states, and most states shifted the burden of persuasion to the defense. Andrea Yates' legal team, for example, had to prove that she was insane when she killed her five children in 2001 - they couldn't simply raise doubts about her sanity.
No federal agency collects data on the number of people who attempt an insanity defense, but experts Crimesider spoke to all said that it is raised in less than one percent of criminal cases. According to Richard Bonnie, a professor at the University of Virginia Law School, the insanity pleas that are successful are usually the ones where the prosecutor agrees that the defendant was insane at the time of the act.
"If you take the insanity defense to a jury, the defendant usually loses," says Bonnie.
Ohio defense attorney Michael Shanks agrees: "I think most juries are reluctant to impose a not guilty by reason of insanity verdict, especially if it's been a violent crime."
And Shanks should know. Last month, his client, Michael Carreiro, was convicted of aggravated murder in the stabbing death of his adopted mother in 2005. Shanks had argued that Carreiro should be found not guilty by reason of insanity. The jury disagreed.
"Most jurors I've talked to would say that if someone has a serious mental illness they should be treated differently" from someone whose criminal act was not the result of sickness, says Shanks. "But that's easy to say, not so easy to do."
On the rare occasions where a defendant is found not guilty by reason of insanity, "law enforcement drops out" and state forensic mental health systems take over, explains Lawrence Fitch, who teaches mental health law at the University of Maryland School of Law.
"Risk assessment is going on all the time," says Fitch. Once the patient's illness becomes controlled, he gains privileges, from walks on the grounds of the hospital, to day passes outside, up to what Hinckley has been granted in recent years, which included several days at a time at his mother's home in Williamsburg, Va.
According to CNN, St. Elizabeth's Hospital in Washington. D.C. has proposed that Hinckley be granted eventual release "at the discretion of the hospital" after completing two 17-day visits to his mother's home, followed by six 24-day visits. On Thursday, the judge in the case said he was reluctant to give Hinckley's doctors the authority to determine his fate.
Fitch says that typically, patients who are granted conditional release are monitored very closely to make sure they comply with ongoing treatment for their mental illness.
"It's kind of like parole but much stricter," said Fitch. "If there is any non-compliance, they go back in. So the recidivism rate tends to be low."
UVA's professor Bonnie told Crimesider that, in his opinion, there is "very little risk" associated with Hinckley's release.
There is no way to know for sure what sentence Hinckley would have faced had he been found guilty of trying to assassinate the president. Sara Jane Moore, who was sentenced to life for firing a shot at President Gerald Ford in 1975 was paroled in 2008 at the age of 77. And Francisco Martin Duran, who was charged with trying to assassinate President Clinton after he fired at least 29 shots at the White House in 1994, was sentenced to 40 years in prison.
According to Willard Oliver, co-author of the book, "Killing the President: Assassinations, Attempts, and Rumored Attempts on U.S. Commanders-in-Chief," Hinckley would likely have gotten at least 30 years in prison, and possibly a term of life, depending on the discretion of the judge.
This issue will likely play out in court soon, as Oscar Ortega-Hernandez, the young man accused of shooting at the White House last month is scheduled to appear in court on Monday. According to a spokesperson for the U.S. Attorney's office in Washington, D.C., Ortega-Hernandez has been charged with trying to assassinate the president, and could face life if convicted.
But Hinckley was not convicted.
"We're not punishing him - he was acquitted," says Fitch. "If he doesn't need to be hospitalized for his safety or our own, why keep him in there?"
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