In 1970, the U.S. Supreme Court gave its approval to a special type of guilty plea, one in which a criminal defendant maintains his innocence while, at the same time, accepting a plea deal from the prosecution.

Those “Alford pleas,” named after the case North Carolina v. Alford, are permissible when a defendant believes it is in his best interest and, the Supreme Court added, when there is “a factual basis for the plea.”

On Tuesday, the Colorado Supreme Court placed Alford pleas under a microscope to answer a question that has divided other state and federal courts. Is an Alford plea constitutional when a defendant pleads guilty, insists he is innocent, but there is not, in fact, strong evidence he is guilty of the charge?

“Alarming rates of people are pleading to things they didn’t actually do,” argued attorney Krista A. Schelhaas, representing Delano Marco Medina in his challenge to his own Alford plea in Lake County. “These are the people who are continuing to say, ‘ I’m innocent.’ And it’s not that we would never accept that plea. It’s that we would verify. The Constitution requires there’s a verification process.”

But some justices observed during oral arguments that defendants may have good reason to plead guilty to an offense they did not commit if it helps them avoid a likely guilty verdict on other, potentially more serious charges.

“I think this case seems to have a be-careful-what-you-wish-for quality when it comes to criminal defendants,” said Justice William W. Hood III.

Medina pleaded guilty to a felony menacing charge, in which the prosecution claimed he held a knife to his victim’s throat. In exchange for a one-year prison sentence, the prosecution dismissed five other traffic and criminal cases against Medina in a “global disposition.”

Medina’s attorney told the trial judge that, in Medina’s “heart of hearts, he does not believe he’s guilty” of menacing, but he was pleading guilty to take advantage of the deal. The defense waived the procedural requirement that there be evidence of guilt, known as a factual basis. The trial judge proceeded with the understanding that Medina had entered an Alford plea and told him he “cannot come back” and change his mind.

Later, Medina attempted to withdraw his plea, claiming he had not understood it and that new evidence would show he did not commit menacing after all. At the same time, Medina admitted he was guilty in his other dismissed cases.

The Court of Appeals examined whether Medina’s plea was knowing, voluntary and intelligent, which is a requirement of due process. A threejudge panel looked to the Alford decision, which involved a defendant who pleaded guilty to murder while maintaining his innocence because a guilty verdict at trial could have resulted in the death penalty. The panel determined Alford did not contain a constitutional requirement for strong evidence of guilt.

While other courts have found that a factual basis for guilt is intertwined with the knowing, voluntary and intelligent requirement, the Court of Appeals opted against placing Colorado in that cohort.

“Given the benefit of the bargain of a ‘very generous’ deal as described by the prosecutor, and Medina’s acknowledgment that he was guilty of some but not all charges in his six criminal cases, this is a situation where competing interests were contemplated and served by a global disposition,” wrote Judge Sueanna P. Johnson in finding Medina’s plea constitutional.

On appeal to the state Supreme Court, the justices acknowledged the safeguard that comes from convicting defendants only when there are facts suggesting their guilt.

“The defendant doesn’t have to admit guilt, but the whole point of saying there’s some factual basis is to ensure we don’t enter a judgment of conviction against an innocent person,” said Justice Richard L. Gabriel.

However, countered Justice Monica M. Márquez, sometimes prosecutors will add a charge for a defendant to plead guilty to, in exchange for dismissing the original charges that were supported by evidence.

“It’s set up in a way to benefit the defendant for potentially other reasons. It seems that your rule requiring a factual basis would prohibit those kinds of plea agreements,” she told Schelhaas.

Schelhaas responded that she was asking the court to resolve a narrow problem: Defendants who believe they are innocent and do not fully understand the consequences of pleading guilty.

She referred to the “innocence problem,” a term used by scholars to describe the act of pleading guilty because of a favorable offer from the prosecution, despite a defendant’s plausible or actual innocence. Belmont University professor Lucian E. Dervan has written that plea bargaining became commonplace during the Prohibition era, and now roughly nine in 10 defendants plead guilty.

“Today, defendants whose guilt is uncertain are offered plea bargains as often, if not more often, than those for whom the evidence is particularly strong,” Dervan wrote in 2012. “Not only are these defendants of questionable guilt offered plea bargains, their bargains are often more generous and, therefore, more irresistible than those offered to defendants against whom the government believes it has a strong chance of success at trial.”

The Colorado Attorney General’s Office argued there is nothing special about Alford pleas, and warned the justices away from imposing any additional requirements to assist defendants who happen to believe they are innocent.

“Doing so would provide a defendant who says the magic words of ‘I’m guilty, but I’m also innocent’ with more rights than any other defendant entering into a guilty plea,” said Assistant Attorney General Grant R. Fevurly.

Ultimately, some members of the Supreme Court were receptive to the notion that trial judges should independently verify there is strong evidence of guilt before accepting a guilty plea from a defendant who maintains his innocence.

“What I infer from Alford,” said Justice Carlos A. Samour Jr., “in order to protect the defendant’s rights, the court has to satisfy itself that there’s some evidence of guilt. That this person the court is allowing to plead guilty ... should be allowed to continue with his plea because there is strong evidence of guilt in the record.”