An ongoing audit at the state's crime lab has revealed more than a year and a half of faulty testing of evidence in shootings, leaving attorneys across South Carolina to grapple with fallout that could disrupt prosecutions.

Scientifically flawed examinations of gunshot residue — which can show whether someone fired a gun — have been found in 34 cases from 13 of the 16 judicial circuits, according to documents obtained from the State Law Enforcement Division, defense lawyers and prosecutors. The preliminary findings prompted the recent resignation of the SLED laboratory analyst that the agency said was responsible.

One of the most widely watched state prosecutions is affected: the murder trial of the North Charleston police officer who shot Walter Scott. But the implications in Michael Slager's case remain uncertain.

Elsewhere, attorneys are scrambling to determine whether convictions were influenced by false testimony from the analyst. They're filing motions to delay trials and asking judges to toss out evidence against potential murderers and attempted killers.

As a man accused of trying to shoot a Richland County deputy was set to be tried last month, attorneys in Columbia became some of the first officials outside SLED to learn about the problem. That trial was delayed, and prosecutors are ordering transcripts of two others that already prompted murder convictions.

"We need to review those trials to ensure that everything was done correctly," 5th Circuit Assistant Solicitor Joanna McDuffie said. "We want to make sure ... the cases were prosecuted fairly based on sound scientific evidence."

Spokesman Thom Berry said SLED planned to ask police departments to resubmit samples for retesting. SLED's lab analyzes such evidence for most agencies in the state. Some counties, such as York and Richland, have their own.

SLED has encountered similar problems before. Three years ago, an agent was fired over allegations that she fabricated a confession in a child death probe. The agency and attorneys had to review other cases she handled.

The impacts of the recent episode could prove negligible. SLED documentation stated that the conclusions of some tests could change little. But in other samples, the examinations might have missed gunshot residue, giving fodder for defense lawyers hoping to challenge the results altogether.

The microscopic particles spewed by a discharged firearm land on hands, clothes and the gun itself, where they can be collected later. The evidence can be helpful for juries when questions are raised about whether someone fired a weapon.

Defense lawyers for Slager, the former officer charged with murder in Scott's killing, are troubled by the development.

They have alleged that Scott grabbed at the lawman's belt, which holds his pistol, during the fatal encounter in April 2015. They pointed to multiple gunshot residue particles on one of Scott's hands as a clue that he might have touched the gun with that hand while holding his cellphone with the other.

But the audit has raised the possibility that each of Scott's hands had multiple particles.

Prosecutors have dismissed suggestions that Scott grabbed at Slager's gun. The officer handcuffed Scott after the shooting, when gunshot residue could have transferred from his hands to Scott's, they explained.

Ultimately, Slager said he fired in self-defense because Scott had taken his Taser. A video showed him shooting as Scott ran away. Slager's murder trial last year ended in a hung jury. He faces a federal civil rights proceeding in May before any retrial in state court.

His case is one of six in the Charleston-area's 9th Circuit that were affected by the flawed tests.

"We do not believe this will constitute a significant issue in the prosecution of Mr. Slager," Chief Deputy Solicitor Bruce DuRant said

The shortcomings in the analyst's work were discovered in early November during a technical review, according to a SLED letter filed in one court case.

The agency then took another look at the 227 cases that the worker had analyzed between 2015 and Nov. 7, revealing problems in 15 percent of them. SLED was considering whether to look back to January 2014, when the expert started doing those tests independently.

It was the employee's first job in law enforcement, S.C. Criminal Justice Academy records showed. SLED reported the discovery in January to the accreditation arm of the American Society of Crime Laboratory Directors.

 “In many instances, this will not have a dramatic impact,” Capt. Wendy Bell of SLED’s forensics operation wrote in letters to the state's elected solicitors. “However, we would like for the case file to represent the most complete analysis possible.”

The most contentious issue for some attorneys is what officials knew and when they knew it.

Many defense lawyers and prosecutors statewide heard about the issue in mid-March. Ninth Circuit Solicitor Scarlett Wilson said she first got a phone call, then the letter from SLED days later.

Savage demanded that authorities divulge whether they "intentionally misled" the defense about the gunshot residue analyst's availability for Slager's trial.

The analyst also was expected to testify this month in the Richland County trial of Arkeem Breeland, who is charged with firing shots at a deputy responding to a domestic disturbance north of Columbia in January 2016.

Gunshot residue was found on his hands, the SLED tests concluded, according to a recent court filing.

Assistant Public Defender Sarah Jurick said samples already have been contaminated by flawed analysis. Retesting wouldn't be reliable, she argued in the filing.

"There is no way to guarantee accuracy at this point," Jurick said.

A judge is weighing a request to throw out the gunshot residue, which the defense dubbed the primary physical evidence against the accused shooter.

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Reach Andrew Knapp at 843-937-5414 or twitter.com/offlede.

Andrew Knapp is editor of the Quick Response Team, which covers crime, courts and breaking news. He previously worked as a reporter and copy editor at Florida Today, Newsday and Bangor (Maine) Daily News. He enjoys golf, weather and fatherhood.