Amid all the other turmoil of the last couple weeks, the Supreme Court delivered a blow to Americans’ rights.

On May 23, the six-member conservative majority ruled in Shinn v. Ramirez and Jones that, in essence, defendants cannot introduce evidence in a federal habeas court (challenging a conviction or imprisonment) that was not already introduced into the state courts’ records, including when the evidence is that the defendants’ post-conviction counsel (lawyer at time of sentencing or appeal) was incompetent.

Shinn v. Ramirez was the case against two Arizona men on death row who had successfully petitioned federal courts to allow evidence of their lawyers’ incompetence after traditional avenues of appeal had been used and denied.

The first defendant, Barry Lee Jones, was convicted of killing his girlfriend’s daughter. He appealed to the Arizona State Supreme Court and lost. Represented by state-appointed post-conviction counsel, Jones filed a habeas petition with an Arizona trial court on the basis of ineffective counsel and was denied. Then Jones filed with the U.S. District Court with new claims of ineffective counsel, saying his trial counsel failed “to conduct sufficient trial investigation … [and] sufficient mitigation investigation for sentencing” and his post-conviction counsel failed to bring up these shortcomings. The district court denied his claim. Jones then appealed to the U.S. Court of Appeals for the Ninth Circuit.

While Jones’ case was pending with the Ninth Circuit, another case, Martinez v. Ryan, was decided by the Supreme Court. The Martinez v. Ryan (2012) decision crafted a narrow exception to the Anti-Terrorism and Effective Death Penalty Act, or AEDPA, and its ruling was reaffirmed in Trevino v. Thaler (2013).

In general, the AEDPA prevents federal courts from holding evidentiary hearings if the defendant “has failed to develop the factual basis of a claim in State court proceedings.” In the cases against Jones and David Ramirez, David Shinn, director of the Arizona Department of Corrections, and Walter Hensley, the warden of the Arizona State Prison Complex-Eyman, contend the AEDPA must be enforced as written and their ineffective counsel appeals denied.

The Martinez ruling said, in the spirit of equity and the Sixth Amendment’s guarantee to the assistance of counsel at trial, that petitioners raising the issue of ineffective or incompetent lawyers would be allowed to introduce new evidence during federal habeas proceedings. The reasoning: Evidence of ineffective counsel is usually in the form of a negative — a failure to investigate a lead, a lack of relevant fact-finding, an omission of information that could have changed the verdict. As such, the “evidence” isn’t in the state record, because it was never introduced when it should have been.

After the Martinez decision, the Ninth Circuit sent Jones’ case back to the district court with the order for it to consider Jones’ claim of ineffective counsel and evidence thereof. The district court found his trial lawyer had failed to introduce evidence that could have cast doubt on Jones’ guilt.

The other defendant, Ramirez, was convicted of killing his girlfriend and his girlfriend’s daughter. His claim of ineffective counsel stemmed from his lawyer’s failure to present evidence of Ramirez’s severe mental disability, which could have kept him from getting the death penalty. His post-conviction lawyer then failed to cite ineffective trial counsel. His case also went all the way to the Ninth Circuit before being sent back to the district court to be heard again under the new rule created in the Martinez decision.

As the Legal Information Institute says, “two rounds of counsel ineffectiveness constitutes precisely the type of extreme malfunction in the justice system that the Martinez decision was intended to correct.”

However, the Supreme Court’s ruling in Shinn, written by Justice Clarence Thomas, reverses the Martinez decision and reaffirms the extremely strict limitations built into the AEDPA. Once again, federal habeas proceedings will be limited to only the evidence or claims introduced during state-level proceedings, even if the additional evidence could exonerate the defendant or change their sentence.

This ruling is especially dangerous for lower-income defendants who can’t afford private lawyers and are instead reliant on public defenders, but it could impact anyone.