Charlie Riedel/AP

The power of the State—of government, in other words—is awesome. And nowhere is that power greater than when it controls life, death, and liberty. The Framers knew this kind of power can corrupt and believed in the principle, articulated much later by Lord Acton, that absolute power corrupts absolutely. They also believed that such power could be grossly misused in the hands not just of individuals acting on behalf of the State but also on behalf of the majority population, creating, in the words of John Adams, "tyranny of the majority." The whole constitutional structure, and the civil liberties built into the first 10 amendments to the Constitution, are grounded in those beliefs.

That immense power over liberty and life is especially evident in the criminal-justice system, in the hands of police and prosecutors. The deep suspicion of governmental power that animates not just the Framers but also philosophical conservatives demands a vigorous effort to curb that power and provide the necessary and appropriate checks and balances to the police and prosecutors who wield it. That effort has rarely been there, with notable exceptions in the libertarian world that I will discuss below.

Why? One main reason is that conservatism has another strain: of intense respect for the existing order, a fear that it can be undermined by crime or disorder, and the belief that police and prosecutors are the front line of protecting that order. Another reason is that the abuses of power are most harmful to those who are weak, limited, and poor, and disproportionately minorities. There is a racial element here, but one does not have to be racist to believe that arrests or traffic stops by police, or stop-and-frisk policies, only occur where crimes have been committed or there is real and reasonable suspicion of same—and that if one is not guilty, one will either go free or suffer the indignity of an undeserved traffic ticket; no big deal. That bigger indignities are suffered by the poor and minorities doesn't resonate for those who have never experienced the problems.

Michael Brown and Ferguson, Missouri, along with Eric Garner, the Staten Island man killed by a police choke hold, have put questions about police misconduct squarely in the public square recently—in Ferguson, not just in the death of the unarmed teen but also in a long history in the county of harassing minorities and shaking them down for money to finance police operations, and in the unsettling pictures of police snipers aiming at demonstrating crowds from tank-like military vehicles. Brown and Garner are only the most visible of countless cases in which these powers have corrupted, and in which the victims are disproportionately minorities but include plenty of non-minorities as well.

Brown's case ignited a major national debate, but other incidents happen every day. Last year, we had the horrific case of John Geer in Springfield, Virginia, shot as he stood, unarmed, inside the front doorway of his house after a minor domestic dispute; when his children and other family tried to administer aid, police allegedly blocked them while he bled to death. A year later, there has been no explanation, no charges filed, no communication from prosecutors or police to his family, which has sued. There are many others, including those where police fired dozens or hundreds of bullets at individuals sitting in their cars.

Shooting deaths are obviously horrific. At the same time and for good reason, we cut police a lot of slack in confrontations; they are in the line of fire, and many officers are killed on duty. But there need to be sanctions for those who abuse their power over life and death, or who clearly overreact. And common police protocols where shooting to kill is the norm, and other means to disable individuals who are threats or perceived threats are not actively encouraged, need rethinking and redrawing.

But cases like Brown, Garner, or Geer, though way too prevalent, are not the only big problem here. The new power of DNA evidence along with the remarkable tenacity of the Innocence Project and other comparable efforts have uncovered hundreds of cases of wrongful imprisonment—and some of wrongful capital punishment. Consider the case of Cameron Todd Willingham. From the mesmerizing account in 2009 by David Grann in The New Yorker to the excellent story in The Washington Post by Maurice Possley of the Marshall Project, it is compellingly clear that Willingham was wrongfully executed in Texas for deliberate arson that killed his wife and children, a crime he did not commit. It is also clear that from prosecutor John H. Jackson, who allegedly manipulated a jailhouse informer to turn on Willingham, to the indifference, at best, of parole authorities and Governor Rick Perry, to exculpatory evidence, there was a shocking level of unconcern or worse about putting to death a man whose guilt was at least in question.

Or consider the case of brothers Henry Lee McCullom and Leroy Brown, who served 30 years in prison for the brutal rape and murder of an 11-year old girl with McCullom on death row, the case that was repeatedly used by Justice Antonin Scalia to justify the death penalty. Both were just released after evidence clearly tying the crime to a man already in prison for another brutal crime. McCullom and Brown were convicted based on the clumsily coerced confession of a young man with an IQ under 60, and with evidence exonerating the two and pointing in another direction that was never brought to the fore by police or prosecutors—a prosecutor who even today, astonishingly, still insists the two were guilty.