I believe they’re referencing this:

The U.S. Supreme Court ruled Monday that state prisoners have no constitutional right to present new evidence in federal court to support their claims that they were represented at trial and on appeal in state courts by unqualified or otherwise deficient lawyers. The vote was 6-to-3, along ideological lines.

. . .

On Monday Thomas wrote the majority decision hollowing out that 2012 ruling on behalf of the court’s new six-justice conservative super majority.

He said that federal courts may not hear “new evidence” obtained after conviction to show how deficient the trial or appellate lawyer in state court was. To allow such evidence to be presented in federal court, he said, “encourages prisoners to sandbag state courts,” depriving the states of “the finality that is essential to both the retributive and deterrent function of criminal law.”

. . .

Writing for the three dissenters, Justice Sonia Sotomayor called the decision “perverse,” and “illogical.” The Sixth Amendment “guarantees criminal defendants the right to effective assistance of counsel at trial,” she said. “Today, however, the court hamstrings the federal courts’ authority to safeguard that right.”

NPR Source

This is so from 2022.

It happened in 2021.

A California father took his two young children to Mexico and killed them with a spearfishing gun after he claimed he had been “enlightened by QAnon and Illuminati conspiracy theories,” federal authorities say.

According to a criminal complaint filed in federal court in California, Matthew Taylor Coleman reportedly told investigators he had been “receiving visions and signs revealing that his wife possessed serpent DNA and had passed it onto his children” and that by killing them he was “saving the world from monsters.”

NPR Source