Over more than a two-decade period, nearly every FBI forensic expert in the agency's microscopic hair analysis unit gave flawed testimony in court against at least 268 defendants, The Washington Post reported in what is turning out to be one of the nation's largest forensic scandals to date.

According to the Post: "Of 28 examiners with the FBI Laboratory's microscopic hair comparison unit, 26 overstated forensic matches in ways that favored prosecutors in more than 95 percent of the 268 trials reviewed so far, according to the National Association of Criminal Defense Lawyers (NACDL) and the Innocence Project, which are assisting the government with the country's largest post-conviction review of questioned forensic evidence."

The organizations are helping the government conduct the country's largest post-conviction review of questionable forensic evidence and released the statistics as part of an agreement to publicly release results after reviewing the first 200 convictions, the Post said.

In 32 of the cases, the defendants were sentenced to death, and 14 have already been executed or died in prison, according to the groups. The Post notes that the FBI errors alone don't necessarily mean there wasn't additional evidence to convict the defendants.

So far, four defendants have been exonerated due to the erroneous testimony, and defendants and prosecutors in 46 states and Washington, D.C., are being notified as to whether an appeal may be warranted.

The FBI and Justice Department told the Post they will continue reviewing all cases and "are committed to ensuring that affected defendants are notified of past errors and that justice is done in every instance. The Department and the FBI are also committed to ensuring the accuracy of future hair analysis, as well as the application of all disciplines of forensic science."

While the FBI is waiting to finish all reviews before assessing causes, the bureau did acknowledge that until 2012, forensic hair examiners "lacked written standards defining scientifically appropriate and erroneous ways to explain results in court," reported the Post, adding that the bureau expects to release standards this year for court testimony and lab reports for 19 forensic disciplines.

An investigation was launched by federal authorities in 2012 after the Post reported that hundreds of people could have been wrongly convicted due to flawed forensic hair matches.

The review found that FBI experts "systematically testified to the near-certainty of 'matches' of crime-scene hairs to defendants, backing their claims by citing incomplete or misleading statistics drawn from their case work."

But in reality, the newspaper said, "there is no accepted research on how often hair from different people may appear the same. Since 2000, the lab has used visual hair comparison to rule out someone as a possible source of hair or in combination with more accurate DNA testing."

One man whose conviction was based on the erroneous FBI hair analysis is Cleveland Wright, who spent 28 years behind bars for a 1978 murder that he did not commit.

"I didn't know anything about forensics," he told CBS News. "I didn't know too much about law when I got arrested and locked up, but I just knew I was innocent."

Wright was exonerated in 2014 but still hasn't been compensated for his time behind bars.

"I just thank God for the people that's looking into these cases; not only mine, other people that are in the same situation that I am in, you know, they need help too, they crying out too, their heart is crying out also," Wright told CBS.