ALBANY, N.Y. – The New York limousine crash that killed 20 people remains shrouded in secrecy nearly a year later.

From public safety probes to legal battles over possible fault, the unanswered questions from the Schoharie County crash cast a pall over the lives shattered by the nation’s deadliest crash in more than a decade.

"A year later, nothing has changed," several of the victims' families said in a statement. "No one has been held accountable for this tragedy, and this delayed justice keeps our families in limbo reliving the traumatic loss of our loved ones."

Donna Rivenburg, whose daughter Amanda died in the crash, said she wants answers.

"I just go day by day waiting for a final outcome," she said.

Central to the unanswered questions is why, according to authorities and court records, a limousine with documented safety problems and improper certifications didn’t get removed from roadways.

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The limo’s owners and operators, including Nauman Hussain, who faces a slew of criminal charges, used it for a job that turned a birthday celebration into a historic tragedy Oct. 6, 2018.

A clash between local officials and federal investigators over analyzing the wreckage has delayed the resolution and potentially compromised efforts to improve limousine safety across the country, federal records show.

Federal investigators issued new safety recommendations Wednesday to improve dangerous seating issues in limousines connected to the Schoharie crash, but they have yet to determine a cause.

“The crash raises a number of important issues that people may not be aware of,” said Russ Rader, a spokesman for the Insurance Institute for Highway Safety, a national group dedicated to reducing roadway deaths. “This was a perfect storm of a lot of bad things happening together.”

Why are the investigations incomplete?

The National Transportation Safety Board criticized Schoharie District Attorney Susan Mallery for stymieing a federal investigation into the crash.

Mallery refused to give NTSB investigators access to the limo wreckage for months, arguing it could disrupt the criminal case. A judge intervened and granted federal investigators access in January, but the delay still looms over the federal safety review.

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“The investigation would be further along had we been able to follow our standard processes for the collection of evidence,” NTSB spokesman Eric Weiss said Sept. 16.

NTSB officials cited concerns about perishable investigative information, such as corrosion on the vehicle’s brakes, being lost because of the delays.

Similarly, the criminal trial for Hussain was postponed to January 2020 – it was initially set for September – in part because defense attorneys cited delays in gaining access to the limo wreckage.

“We are still seeking justice and hoping the investigation and prosecution prevents tragedies like this from occurring in the future," the families' statement read.

Was it the brakes?

Though an official cause hasn't been determined, a state expert’s report concluded the 2001 Ford Excursion stretch limo's brakes failed as it barreled down a hill on Route 30, killing all 17 passengers, the limo driver and two pedestrians.

Many details about the condition of the limo’s brakes and overall maintenance remain unclear, court records show.

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A roadside Department of Transportation inspection of the limo in March 2018 determined at least 25% of the brakes were defective and a hydraulic brake line was constricted, resulting in it getting an “out-of-service” sticker, court records show.

After that inspection and before the crash, a Mavis Discount Tire shop allegedly performed repairs on the limo’s mechanical defects, including its brakes, according to a lawsuit filed against Mavis and officials of Prestige Limousine and Chauffeur Services, the limo business.

State agencies denied requests for all the limo’s inspection records, citing exemptions to Freedom of Information Law, said attorney Paul Davenport, representing family members of Erin and Shane McGowan, newlyweds from Amsterdam killed in the crash.

“All the victims deserve justice and deserve to know what happened here and deserve to know who was responsible,” Davenport said.

Mavis contended it "bears no legal responsibility for this tragedy and the events that led up to it, and we will defend ourselves vigorously against all claims."

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The DMV declined to answer questions about its oversight of the Mavis shop, citing pending litigation. It didn't immediately answer USA TODAY Network requests for public records related to the limo crash.

What happens next?

The NTSB's new safety recommendations focus on the lack of lap-and-shoulder seat belts in limousines, as well as modifications made to stretch models that reduce the chances passengers can survive crashes.

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It’s unclear when the NTSB will release its final report on the cause of the crash, and potentially additional safety recommendations.

Follow David Robinson on Twitter: @DRobinsonLoHud