In 2006, Assistant U.S. Attorney Brett Grayson lined up more than 30 jailhouse informants to testify that they had sold drugs to Church Point, Louisiana homemaker Ann Colomb and her three sons. (I wrote about the Colomb case in the May 2008 issue of Reason.) Grayson had used some of these snitches before, in the trial of a Houston drug kingpin. After the Houston trial, Grayson was notified that several of his informants had lied, and that there may have been an information sharing network and perjury ring inside the federal prison system. No matter. Grayson used them again. Colomb and her sons were convicted, and spent three months in prison.

The Colombs were eventually freed, with all charges dismissed. Grayson's jailhouse snitches had lied again, and this time, federal judge Tucker Melancon ordered an investigation into new evidence that, somehow, portions of Grayson's case file were being distributed through federal prisons in Texas and Louisiana. The Colombs, meanwhile, spent their life savings on their defense, and were never compensated. According to defense attorneys, Grayson said at one point during the trial that it didn't matter if he personally believed his snitch witnesses, it only mattered what the jury believed, a notion he articulated again in his closing argument.

I thought about the Colomb case while reading the transcript of the oral arguments in Pottawattamie v. Maghee, heard last Wednesday before the U.S. Supreme Court (read my previous column on the case here). The case turns on whether prosecutors who knowingly fabricate evidence to convict an innocent person should be susceptible to lawsuits, or if prosecutors should always have absolute immunity from such suits, no matter how bad their behavior.

During the hearing, Deputy Solicitor General Neal Katyal argued that "if prosecutors have to worry at trial that every act they undertake will somehow open up the door to liability, then they will flinch in the performance of their duties and not introduce that evidence." Katyal made similar statements throughout the hearing: "When someone is introducing evidence at trial, you don't want to chill them in the performance of their duties in any way," and "the overriding interest is protecting the judicial process and not letting information be chilled and not come in." Chief Justice John Roberts underlined that formulation, twice inquiring as to the "chilling" effect of stripping immunity for prosecutors.

It took new Associate Justice Sonia Sotomayor to make the obvious point: We want prosecutors to "flinch" before introducing evidence they suspect might not be true. In fact, we want them to not introduce that evidence at all. And there should be a chilling effect on misconduct as egregious as coaching witnesses to lie. If Brett Grayson had known he could be held liable for his parade of lying jailhouse snitches, perhaps he'd have vetted their stories a bit more carefully, or been more vigilant about ensuring that portions of his case file didn't somehow get passed around the prison system.

The amount of liability the would-be plaintiffs in Powattattamie want prosecutors to shoulder is minimal. The Supreme Court has held for 30 years that even prosecutors who knowingly withhold exculpatory evidence in a case that results in the conviction of an innocent person can't be sued for damages. The wrongfully convicted men in Powattattamie aren't even seeking to undo that. They're asking that prosecutors who knowingly fabricate evidence against an innocent person, then use that evidence at trial, be susceptible to a lawsuit. And even there, prosecutors would still be afforded the qualified immunity given to police officers, which means potential plaintiffs would still have a high hurdle to clear before getting into court. (It's worth noting that the prosecutors in Powattattamie weren't sanctioned or disciplined in any way, which is about par for the course in the criminal justice system.)

The problem here is that the Supreme Court has painted itself into a corner. While the Court has always upheld absolute immunity for prosecutors while trying a case, it has ruled that prosecutors who help investigate a case—that is, who act as police officers—should receive the same, reduced qualified immunity given to cops. But here's where it gets messy. At what point is a prosecutor acting as a prosecutor, and at what point is he acting like a cop? The roles have been muddied over the years.

Consider snitch testimony. Under federal law, only a federal prosecutor, and not a federal police investigator, can gauge whether information offered by a jailhouse snitch is useful enough to offer time off the informant's sentence in exchange for his testimony. That means prosecutors are put in the role of interviewing potential informants to determine whether the stories are plausible (or, if they're less scrupulous, merely whose stories are most damaging to the defendant). This is more the role of an investigator than the prosecutor of a case.

Solicitor General Katyal and the attorney for the prosecutors in Powattattamie both made the absurd argument that the actual injury in Powattattamie occured when the defendants were wrongly convicted and jailed, not when the evidence against them was manufactured. Therefore, because the prosecutors were acting in their role as triers of the case when the injury occurred, they should be immune to lawsuit, even though they were acting as investigators when they conjured up the perjured testimony in the first place. Had they passed the evidence off to another prosecutor for trial, they could still be sued. This led Justice Anthony Kennedy to ask, "so the law is the more deeply you're involved in the wrong, the more likely you are to be immune? That's a strange proposition."

It certainly is. Katyal went so far as to argue that even police officers who manufacture evidence used to convict an innocent person may not be liable, so long as they tell the prosecutor ahead of time that the evidence has been faked—again because the actual injury occurs at the time of conviction, and at the time of conviction the state actor inflicting the damage is the prosecutor acting in his role as prosecutor, at which point he has immunity. Kennedy reiterated the problem: "Again, the more aggravated the tort, the greater the immunity."

Katyal went on to argue that there is no "free-standing due process right not to be framed," a striking line that made it around the Internet last week. If you're a constitutional originalist, that statement isn't quite as controversial as it first sounds: An originalist may believe that the Constitution protects us from government overreach, but it doesn't explicitly lay out a method of recovering damages for government violations of our rights; that's left up to Congress.

The problem with the originalist interpretation is that the Constitution's authors surely would have hoped for and expected at least some relief. The Bill of Rights both establishes a civil courts system to allow citizens to recover damages from one another, and lays out a clear set of rights that government officials aren't permitted to abrogate. It makes little sense to think, then, that the document would be consistent with the notion that government officials could systematically violate two citizens' rights in a way that resulted in significant injury (in this case, 26 years in prison), and yet be wholly immune from those citizens' efforts to collect damages, simply because Congress failed to legislate a path to relief.

One of the notable things about this case is that the pro-law enforcement position was argued by Katyal, an official in the Obama administration, while the pro-defense, anti-executive branch position was argued by Paul Clement, the former solicitor general for the Bush administration. The Obama administration has consistently taken the pro-prosecution side in criminal justice cases since Obama took office, confirming that where the rubber meets the road on issues related to police powers and the rights of the accused, what matters most is not political ideology but who holds the reins of power.

Clement's toughest questioning came from the Court's two Bush appointees, Chief Justice Roberts and Justice Samuel Alito. But Clement rather brilliantly concluded his time with a direct challenge to the two Bush-appointed justices that probably won't affect either's ruling, but at least ought to make them squirm. Keeping prosecutors immune from liability, he argued, is a classic case of judicial activism.

The phrase "absolute immunity" appears nowhere in the Constitution, nor does it appear in Section 1983, a part of the federal criminal code that provides a way for citizens to collect damages against the government. The Court read absolute immunity into the law in the 1976 case Imbler v. Pachtman because it feared the ramifications of prosecutors being susceptible to lawsuits. As Clement argued, there is "no common law support at all for absolute immunity. And I wouldn't think that this Court was particularly interested in coming up with implied immunities that aren't in the statute and had no basis at the common law, and that's why I think some of the Justices that have looked at this as an original matter have tended to be quite reluctant in recognizing absolute immunity because it lacks support in the text."

So while for most of the hearing the Court and litigants took absolute immunity as a given and debated whether and how to carve exceptions into it, Clement concluded by pulling the sheet back on absolute immunity, period. In doing so, he cleared a path for the justices to revoke absolute immunity altogether, or at least severely limit the concept. That almost certainly won't happen. But it should (but probably won't) give the Court's conservative wing some cover to at least poke enough holes in prosecutorial immunity to discourage the more egregious examples of misconduct.

Radley Balko is a senior editor at Reason magazine.