DETROIT (AP) — The Michigan Supreme Court on Wednesday rejected a last-chance effort to revive criminal charges against seven people in the Flint water scandal, waving away an appeal by prosecutors who have desperately tried to get around a 2022 decision that gutted the cases.

The attorney general’s office used an uncommon tool — a one-judge grand jury — to hear evidence and return indictments against nine people, including former Gov. Rick Snyder. But the Supreme Court last year said the process was unconstitutional, and it struck down the charges as invalid.

State prosecutors, however, were undeterred. They returned to Flint courts and argued the charges could be easily revived with a simple refiling of documents. That position was repeatedly rejected all the way to the state’s highest court.

“We are not persuaded that the question presented should be reviewed by this court,” the Supreme Court said in a series of one-sentence orders Wednesday.

There was no immediate response to an email seeking comment from the attorney general’s office.

Orders were filed in cases against former state health director Nick Lyon, former state medical executive Eden Wells and five other people.

Snyder was charged with willful neglect of duty, a misdemeanor. The indictment against him has been dismissed, too, though the Supreme Court did not address an appeal by prosecutors Wednesday only because it was on a different timetable.

Managers appointed by Snyder turned the Flint River into a source for Flint city water in 2014, but the water wasn’t treated to reduce its corrosive impact on old pipes. As a result, lead contaminated the system for 18 months.

Lyon and Wells were charged with involuntary manslaughter. Some experts have attributed a fatal Legionnaires’ disease outbreak in 2014-15 to the water switch. They were accused of not timely warning the public.

Indictments were also thrown out against Snyder’s former chief of staff, Jarrod Agen; another key aide, Rich Baird; former Flint Managers Gerald Ambrose and Darnell Earley; former city Public Works Director Howard Croft; and former health official Nancy Peeler.

Snyder acknowledged that state government botched the water switch, especially regulators who didn’t require certain treatments. But his lawyers deny his conduct rose to the level of any crime.

Prosecutors could try to start from scratch. But any effort to file charges in a more traditional way against some of the targets now could get tripped up by Michigan’s six-year statute of limitations.

Since 2016, the attorney general’s office, under a Republican and now a Democrat, has tried to hold people criminally responsible for Flint’s water disaster, but there have been no felony convictions or jail sentences. Seven people pleaded no contest to misdemeanors that were later scrubbed from their records.

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