i'm looking at them under the microscope and they have enough characteristics where i can say with reasonable scientific certainty that these two hairs match. >> they believed in what they were doing, but they were not scientists. it wasn't science at all. at all. >> joseph was at least the 74th american exonerated of a crime in a case involving the forensic science of microscopic hair analysis. >> it's not science to visually examine something and say they're the same. that's not science. that's subjectivity. >> the u.s. department of justice is now reviewing thousands of old convictions containing hair analysis testimony. last april, it released a devastating assessment. in the cases reviewed, fbi testimony about hair evidence was scientifically invalid 95 percent of the time. >> this is a virus that escaped from the fbi crime lab and it infected the entire criminal justice system and it's going to take a lot of work to undo it. the integrity of the criminal justice system is at stake. plain and simple. >> this is the story of how, for years, the fbi used an untested forensic method in courtrooms across the country. and of the men who paid for it -- with decades of their lives. [crowd cheers.] >> in january 2015, joseph sledge walked out of prison for the first time in over 37 years. >> did you ever think this day was coming? >> oh yes, i did. yes, there wasn't no doubt. >> he moved back to his hometown of savannah, georgia. we met him one morning on the river, where he likes to go crabbing. >> if by chance we caught a crab, it'd be an act of god. >> aw cause, when we was coming up, that's all we did. our daddy took us on the dock, catching crabs. we had a good life coming up. we did, you know. yes we did. >> joseph's sister barbara also lives in savannah. >> that's him, mom and him. >> barbara was in her twenties when joseph went to prison. >> he didn't get a chance to see his daddy when he passed. you know, i had to write him and let him know daddy passed. had to write him a letter and let him know mother passed. had to write him a letter and let him know grandmamma passed. >> a little crab, trying to get out. trying to get out the basket. in north carolina prison. a little crab trying to get away. trying to get away clean, lord. trying to make a move. to find salvation. >> during his time in prison, joseph filed more than twenty-five motions proclaiming his innocence. finally, in 2000, he wrote to attorney christine mumma. she agreed to take up his appeal. >> i believe that joe's life didn't have much value to anybody. and i think he was completely discardable. >> joseph's ordeal started in september 1976, outside a small north carolina town. >> here in the woods near elizabethtown, north carolina, in 1976, a brutal murder happened in this house. >> one sunday morning, two women - a mother and daughter - were found beaten and stabbed to death. within days, police apprehended joseph. the night before the murders, he had walked out of a nearby minimum security prison camp, where he was serving time for stealing clothing. >> that's where my nightmare began. september 5th, 1976. never forget it. >> joseph was charged with double homicide. at his trial, the prosecutor presented two jailhouse informants, who said that joseph confessed to the killings. they received a combined $5000 dollars as reward, about $20,000 in today's money. >> there were a lot of red flags in joe's case. the use of jailhouse informants is always a red flag. >> but the physical evidence didn't add up either. >> the murder scene in this case was, there was blood everywhere. it was on the refrigerator, it was on the walls, it was all over the floor. they were covered in blood. the perpetrator dripped blood throughout the house. and yet there was no blood on joseph's clothing. the bloody palm prints that were found on the floor on either side of the sexually assaulted victim's head um, did not match joseph sledge. they knew they excluded joe sledge. so they just didn't disclose it. they didn't give it to the defense and they didn't give it to the jury. >> this is deputy sheriff phillip little, who collected the evidence from the crime scene in 1976. >> [phone rings] hello? >> hello, i'm calling for phillip little? >> speaking. >> little still lives in elizabethtown, not far from where the murders happened. >> looking at the dynamics of the case when i was investigating it, i wouldn't say mr. sledge is completely off the table. >> but was there any physical evidence connecting joseph sledge to this murder? >> i'm not going to get into that. >> but wouldn't there be one of his fingerprints in the house if he did it? >> not necessarily. >> or the palm prints that were beside the body might match? >> i don't want to get into that. i don't want to get into the evidence. >> there was no physical evidence tying joseph to this crime. the microscopic hair comparison was the closest they could come. >> at joseph's trial, the prosecutor introduced to the jury a group of hairs found at the crime scene. >> how was the hair evidence introduced? >> it was an fbi agent from the fbi forensic laboratory. and he gave an elaborate explanation that the pubic hair that was recovered from the scene was microscopically similar to mine. microscopically similar. >> an agent from washington d.c. testified that hairs found on one victim were quote 'microscopically alike in all respects' to joseph's hair. >> you had the federal bureau of investigation. that's like, that's wow factor to a jury. you put a federal forensic scientist on the stand and god whatever they say, that has to be true. >> the agent also said that hairs "do not constitute a basis for positive personal identification". but the jury was convinced. >> what do you remember about the fbi agent that was brought in to testify about it? >> he was persuasive enough, along the testimony of the witnesses, to lead the court to believe that i was guilty. >> without the hair testimony you say they just... >> they don't got no case. period. >> what were you actually sentenced to? >> two natural life sentences, running consecutive. how could you do one life? you can't do but one. can't do two. >> you know, it would be one thing if you just had this one amazing story, and it was an exceptional situation. but it's, unfortunately it's not. >> watch more "faultlines" on demand or visit aljazeera.com/faultlines. >> this was the worst civil engineering disaster in the history of the united states. >> 10 years after hurricane katrina. >> it was like a nuclear bomb had gone off - everything smelt like dead bodies. >> one constant. >> music has been the essence of this city. >> inspires a community to rebuild its city. >> we gonna bring this city back one note at a time. >> and overcome hard times in the big easy. >> we are bigger, we're better, we're stronger. >> here are the headquarters of the nation's crack law enforcement agency: the federal bureau of investigation. the bureau maintains the most modern and completely equipped crime detection laboratory in the world. >> the discipline of microscopic hair comparison was developed not by scientists, but by law enforcement. >> comparisons show that the strand of hair from the assailant's scalp is exactly the same as the hair of one suspect being held by police. >> the fbi pioneered hair analysis, and used the technique across the country for over fifty years. >> hair microscopy involves two things. one is that a properly trained hair comparison expert can make an association between a hair found at a crime scene, and a suspect hair. >> even a single hair may supply evidence! >> and then two is: is it possible to give a scientifically valid estimate as to how rare or how common that association would be. so in other words, could 1 in 5 people have left this hair? or 1 in 5 million people? >> the examiners trained eye can learn many things. is it human hair? of what race? animal hair? what family? >> it wasn't really until after world war two, when the fbi set up a professional crime lab, where the evidence really began to take a foothold in the prosecution of criminal cases. >> from a microscopic examination of hairs, we can determine race, body area... >> morris samuel clark was the head of the fbi hair and fiber unit in the 1960s and 70s. he retired in 1979, and moved to rural virginia, where we met him at his home. >> where hairs are involved, it's usually a crime of violence. horrible crimes and horrible people involved. >> did you go into court and, and testify about hair analysis? >> oh yes, very, hundreds of times. >> hundreds of times. >> the microscopic hair comparisons the way the fbi did it, was based on approximately 16 different characteristics. the pigment distribution, the structure of the medulla. >> when you would lay out all those kind of say 16 factors in a hair, was there a database of hair to compare that to? >> no. we always had to state that it was not a basis for positive personal identification. >> is there any way to say what the odds would be though of two hairs being, matching 16 factors against 16 factors? and yet still from two different people? >> no. >> we really have no idea how um, the characteristics of hair are distributed in the population. what's incredible and what would surprise people is that hairs on your head are not the same. that there is variation in one individual's hair. >> the hairs on your head are quite different depending on where they're selected. >> doctor terry melton is the founder of mitotyping technologies, a dna lab in pennsylvania. she conducted the test that led to joseph sledge's exoneration. >> if you think about the way microscopy is done on a hair, someone is deciding what color is that hair. microscopy is a very subjective science. and dna is exactly the opposite. you have atcgt and in the other sample you have atcgt. you line those 800 dna bases up next to each other, there's no gray area. >> when scientists figured out how to extract dna from hairs, in the late 1990s -- the fbi stopped relying on hair comparison evidence. but by that point, the bureau had introduced it at trials for decades, influencing thousands of convictions. in 2012, doctor melton's testing overturned two of those convictions, here in washington dc. both men had spent over twenty years in prison. >> i was arrested in august of 1978. >> and when did you go in, kirk? >> i went in, in '82. >> kirk odom was arrested for rape when he was 18 years old. santae tribble for murder, when he was 17. at odom's trial, an fbi agent testified that his hair matched hairs found on the victim's clothing. >> they say that it matched. >> what was going through your mind when they said that? >> foul language. foul language, you know really foul language. >> the agent said he had performed thousands of examinations, and this result was a very rare phenomenon. >> they would describe, with a kind of veneer of statistics, how rare it was by talking about their own experience in the laboratory. >> sandra levick is the public defender who represented both odom and tribble in their appeals. >> they would use terms like 'it's very rare, it's highly unlikely'. it conveyed to the jury a sense that this was statistically valid in some way. >> they said they matched my hair in all microscopical characteristics. and that's the way they presented it to the jury. and the jury took it for granted that that was my hair. >> at tribble's trial, the fbi agent told jurors that he identified a set of human hairs on a stocking cap near the crime scene. but when levick had those hairs dna tested, she got very different results. >> we had all 13 of the hairs that the fbi had examined. they were sent off to terry melton at mitotyping. nine of the hairs had come from the same source. a couple had come from different sources. and one was a dog. >> two different fbi agents who had looked at that and analyzed it, didn't recognize that it was dog hair? >> it was a canine. it was a domestic dog, yes. >> my personal conclusion was the dog committed the crime. (chuckle) >> but now how do you reconcile that in your mind though? >> yeah. how about that? this was the expert witness from the fbi. >> watch more "faultlines" on demand or visit aljazeera.com/faultlines. he quick cuts, beyond the sound bites. we're giving you a deeper dive into the stories that are making our world what it is. >> ray suarez hosts "inside story". only on al jazeera america. >> the idea that there might be problems with fbi forensics is nothing new. twenty years ago, an agent named frederic whitehurst blew the whistle on the science lab there, saying that there were major problems then. he's now out of the fbi, and he lives here in bethel, north carolina. we're on our way to meet him now. >> frederic whitehurst is a forensic scientist who joined the fbi lab in 1986. >> we're putting human beings in cages and death chambers. fellow citizens based on garbage. >> in the mid 1990s, whitehurst alleged that over a dozen fbi agents had performed false or sloppy forensic work. >> whitehurst, you may remember, was the fbi chemist who blew the whistle on shoddy work at the bureau's famed crime lab. >> i'm a law enforcement officer. if i see violations of the law, abuses of authority, corruption or whatever, i am required to report those. >> in response to whitehurst's claims, in 1997, the inspector general of the justice department released a bombshell report. >> the justice department's final report documented example after example of what it called scientifically flawed and inaccurate testimony. >> i think it is highly inappropriate for the fbi to manipulate scientific data in order to obtain a conviction. >> the justice department realized there were broader implications. >> david colapinto is fred whitehurst's lawyer, who closely monitored the justice department's response. >> and what they did was they set up a force of, a task force of criminal lawyers to go through and review all of the cases handled by 12 or 13 examiners mentioned in the ig report. >> in the wake of the report, the justice department vowed to review all cases called into question -- including hundreds involving hair and fiber evidence. >> even more disturbing, the bureau acknowledged the findings have prompted a review of hundreds of other cases for possibly faulty lab work. justice officials insist they will give defendants anything where there is even the slightest doubt it could help them. >> but seven years later, in 2004, the doj ended the review. it never issued a final report. and it never notified the defendants whose cases were under review -- or their attorneys. in the hair cases in question, not a single conviction was overturned. >> the justice department and the fbi were officially stating that they had looked at the cases, and they had found nothing, and no one's convictions had been overturned. >> though there have been 74 dna exonerations in hair cases -- to date, none of them have been prompted by justice department review. instead, they have been achieved by the detective work of outsiders. >> well, in about 2008, i guess it was, i got a call from sandy levick, an attorney up in washington, dc, who was representing a man named donald eugene gates. >> donald gates was the first hair case that sandra levick challenged. in 1981, gates had been convicted of rape and murder in washington. >> she said, 'do you have any information on a man named michael malone?' i said, 'i've got 7gb, i'll send it to you on a flashdrive.' >> michael malone was the fbi hair examiner who had testified against donald gates. whitehurst had named him in 1997. just three years later, the justice department had identified donald gates' conviction as potentially a mistake. but no one notified gates, or his original lawyer. >> you had the complete picture of the identification of mr. gates, the correspondence between the fbi or the doj and the us attorney's office, and then we knew of the failure to inform anybody. >> in 2009, dna testing exonerated donald gates. he had served 27 years in prison, at least nine of them since the doj first flagged his case. >> none of these individuals was contacted. none of the defense lawyers was contacted. again, they were sweeping it under the carpet. knowing that they had people that had been locked up for 10, 15, 20, 25 years. it seemed like they should have been rushing to the defense attorneys saying, you know, we might have a problem. >> nobody wanted to deal with this problem. nobody wanted to confront what it really meant. it doesn't enhance your career to look into cases and, and start stirring around the dust in a 30 or 25 year old rape murder case. >> there's a whole lot of people behind bars in the same situation. there's a whole lot of people all over this country in the same situation. >> in 2012, the department of justice promised finally to conduct a thorough review. it has since identified nearly 2500 cases in which hair comparison evidence was crucial to conviction. in the cases reviewed so far, the justice department found that 26 out of 28 fbi examiners made false claims at trial. >> so we can now say based on a statistically sizable sample of cases that they have reviewed, that they were wrong 95% of the time. >> the department of justice and the fbi refused to speak on camera for this program. publicly, they say they will notify defendants' counsel in cases they review. but they will not release the names of those defendants to the public. at least fourteen of them have already been executed, or died of old age. >> there's a lot of lives at stake. there's a lot of lives at stake, a lot of innocent people. >> why, why is there no sense of urgency? there really needs to be a sense of urgency. people are dying in prison. >> as of april 2015, the doj says that it has reviewed 1800 cases. but in 40 percent of them, it closed the review not because it found no error -- but because it failed to obtain the documents needed to review the case at all. in 2014, while joseph sledge was still in prison, the department of justice reviewed his case. it decided that it did not meet the standards for invalid hair testimony. >> based on the federal bureau of investigation's review of microscopic hair cases and what they're looking for in testimony, they didn't feel joe's case fit the criteria for questionable testimony. >> in other words, joseph sledge's trial was one of the five percent of cases in which the justice department says the fbi got it right. >> that was a case where they didn't overstate the probative value of hair comparison evidence. they were just wrong. wasn't his hair. >> it would pass this current review. >> yes. >> and still it was just wrong. >> just wrong. >> all my real close friends have done died, done died. gone to the grave. >> what could they do to make this right for you? >> give me 40 years. >> give you 40 years. >> yeah of my life. that'd be great. i could use that. >> the lifeline of the american west. >> what does this river mean to you? >> the river, to me, means homeland. >> in danger of running dry. >> there'll come a time when we fight over every last drop of water in the river. >> where's the water going? >> i worry about the future generations - what are they going to have? >> faultlines investigates the shrinking colorado river. >> no group of people can have their american dream... we have to pay that price. >> searching for clues and answers after a bomb blast kills 20 people. you are watching al jazeera. coming up in the next half hour, sri lanka's former president is unlikely to lead the next government following the country's general election. the rebel leader signs a peace deal, but his rival says he needs more time. plus