On Monday, California became the fifth state to allow physician-assisted suicide. With Gov. Jerry Brown’s approval—guided, he admitted, by the consideration of “what I would want in the face of my own death”—the practice is now legal in a state of almost 40 million people, nearly 13 percent of the U.S. population. The law includes safeguards to protect against unwilling death, including an examination of the patient’s mental state and a prognosis of six months or fewer by two doctors, but they did not quell criticism. Critics are concerned about the potential for elder abuse, the dangers facing depressed people, and the risk that disabled people, as well as cash-strapped patients and providers, will face increased pressure to end life. But California’s choice is not without precedent; Oregon, for example, has had such a law in effect since 1997. Some of these predictions, then, can be checked against history.

One finding—striking, albeit not surprising on reflection—is that suffering cannot easily be defined by outsiders. A 2011 study involving interviews with 31 patients who had requested either euthanasia or physician-assisted suicide revealed that the decision to end life is driven not only by pain and fatigue, which might be apparent to observers. Other factors, like personality and life history, are also consequential: how patients understand and narrate their own lives, how they view their relationships to others, how they view their past, present state, and likely future. This has consequences for how physician-assisted suicide is justified: sometimes support takes the form of an argument from compassion, the claim that it is more humane to end unbearable suffering than to prolong it. But if the kind of suffering that motivates a person to end her life cannot be determined by observers, then the compassion-based argument must be supplemented by one based in patient autonomy.

This, of course, is the reason why such laws contain provisions designed to guarantee that the patient is making a voluntary choice. One major such protection is an evaluation of the patient’s mental state. Opponents of the California law cited a risk to patients suffering from depression, but a 2008 review of Oregon’s experience found that “most patients who request aid in dying do not have a depressive disorder”—only one in six of those patients who received a prescription for lethal drugs. Still, the research on this is not totally conclusive: even the 2008 study deemed Oregon’s safeguards insufficient, and a 2011 study raised methodological concerns about earlier work, arguing that there is reason to believe Oregonians with depression are being cleared for assisted suicide.

Other research on this question has attempted to record with greater precision the public’s conflicted feelings. Although some critics have portrayed the pro-legalization position as an elite, largely white consensus, the reality is more complicated. It is true that in 2013, Pew recorded major racial disparities on physician-assisted suicide for terminally ill patients: white Americans approved 53-44, but Hispanic Americans and African Americans both disapproved by two-to-one margins.

That, however, is not the whole story. Another 2013 poll asked respondents for their opinion on the “moral right to suicide” in different situations. Approval was low when the reasons were “burden on family” and “ready to die,” but when the situation was “great pain, no hope of improvement,” Americans largely approved: 62 percent of all adults, 65 percent of whites, 52 percent of blacks, and 58 percent of Hispanics. And despite staunch opposition to assisted suicide by the Catholic Church, 63 percent of Catholics approved.

These numbers are consistent with growing public support for physician-assisted suicide: Gallup’s most recent poll recorded a 10 percent increase in support just since last year. These numbers might help predict the future of assisted suicide in the United States, but a still-more consequential test of public support could come as soon as next year. This is California, after all: opponents of the law are organizing a referendum on the 2016 ballot.