>> get my life together. i keep trying. oh, man. just hurts. >> and big dog 28's survival comes down to the wire. >> down two hands. and we have a broken rotary cable. pull on that [ bleep ]. [ siren wailing ] >> i felt like i was in a war zone with the explosions, the smell of smoke, the smell of burning flesh, people screaming. >> narrator: it was the single most deadly automobile accident in american history -- 99 vehicles, most of them destroyed. 12 people died. >> identifiable? >> no. not at all. >> narrator: more than 50 were injured. >> total destruction. if i hadn't been there and eyewitnessed it, i don't believe i could have believed it. >> narrator: the accident happened along a three-mile

stretch of highway long known for dense, thick fog. but what was causing the fog? the victims and their families wanted answers. the accident occurred on interstate 75 in tennessee on a portion of highway between chattanooga and knoxville. the highway was constructed through a valley which lies between the cumberland and great smoky mountains. from the time the highway first opened back in 1973, there had been numerous multi-vehicle chain-reaction accidents in the

same three-mile section. the first occurred just four months after the highway opened. 3 people died in a 17-car pileup. 10 were injured. just one month later, there was a nine-car accident. although there were no deaths, nine were injured. >> during the first six years the highway was open, there was an average of one multi-car accident each year. one of the largest was in november of 1978, involving more than 60 vehicles. 6 people were killed, nearly 100 injured. all of the accidents had one thing in common -- the sudden appearance of a dense, thick fog, reducing visibility to near zero. tennessee state highway officials responded by installing fog-warning lights to warn drivers when fog was in the area. highway patrol officers were posted to stand watch every morning along the fog-prone area

to make sure drivers slowed down when the fog-warning lights were activated. the combination of these two systems worked. for 11 years, there were no major accidents along the fog-prone stretch of interstate 75. but all of that changed on december 11, 1990. >> it's a massive wreck. everybody's bumping into everybody. >> i've had several reports. i've had an explosion in that area, and they're still piling up. >> as i rolled down the window, i could hear the cars just crashing into each other one after another. >> a motor home hit the front end of my truck just seconds after i had gotten out. and then vehicles started hitting the back of it. i'll never forget hearing one. and he hit other cars and just knocked him out of the way like they were nothing and came and crashed just to the right of that motor home. the explosion was such that it almost knocked me down. >> narrator: mike curtis pulled this 14-year-old boy out of the

motor home, then rescued the boy's mother. >> and i turned and went back to get her husband. all i could see was fire. i could smell hair burning. his coat came off burning in my hands. that's probably the hardest thing i've ever had to witness... the most helpless feeling i've ever had. >> narrator: the man burned to death. 12 people were killed, 56 others injured, making it the largest vehicular accident in american history. these pictures were taken shortly after the accident, when most of the fog had dissipated. >> the vehicles that i saw, i don't even know if you could classify them as vehicles. what normally was a pickup truck was 3 foot in length, bodies still in it.

>> narrator: after 11 years without a serious accident, the killer fog had struck again. but why? the families of the dead and injured demanded answers. they wanted to know what caused the dense, thick fog on december 11, 1990.

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>> narrator: on december 11, 1990, 30-year-old craig piper was driving his tractor trailer south on interstate 75 on his way to visit his mother for the holidays. when he entered the thick, dense fog, visibility was near zero. within seconds, he crashed. [ tires screech ] [ glass breaking ] [ horn blaring ] [ siren wailing ] >> the flames were extremely dense, and i knew there wasn't any way i could get him out. i had to stand there and watch this man burn in his vehicle. there wasn't really anything i could do. i didn't have a fire

extinguisher. i just had to stand there and watch this man burn alive. >> narrator: craig piper's mother wanted answers and hired attorney doug fees, who was not only a lawyer but also an engineer. she wanted fees to find out what caused the terrible fog that was responsible for her son's death. >> she said that the two people in that car were killed and that her son had been burned alive in his tractor trailer and was wondering if there was anything that i could do to help her. >> narrator: the accident occurred along interstate 75 at its lowest point in the valley, about a half mile from where the interstate crosses the hiawassee river. because of its location, fog has always been common in this area. fog is basically a cloud which forms on the ground. fog occurs when there is too much water in the air for the atmosphere to absorb. since cooler air holds less moisture than warm air and cool

air gathers in low-lying areas, the valley through which interstate 75 passes is perfect for the formation of natural fog. but the fog described by the accident victims was extremely thick and dense. was the fog on the day of the accident naturally produced or was it caused by one or more of the local industries nearby? >> on those three days, there was some amount of river fog, although it was relatively small. on all three days, there was a very noticeable emission of fog-related water vapor from the bowater facility. >> narrator: the bowater paper company is located three miles to the east of the interstate highway. it is the largest producer of newsprint in north america and releases large quantities of water vapor into the atmosphere 24 hours a day, as part of the

manufacturing process. wayne davis recommended that the state of tennessee conduct a more detailed study in order to understand the cause of the fogging conditions. the state decided not to fund a more detailed study but elected to install a fog-warning system along the highway and posted state troopers to patrol the fog-prone stretch of highway each and every morning. for 11 years, the system worked. between 1979 and 1990, there were no serious multi-vehicle accidents along the three-mile stretch of interstate 75. the system worked... until december 11, 1990. the wayne davis study was an important starting point for doug fees. but the davis study was conducted 12 years earlier. fees needed to know what caused the fog on december 11, 1990. doug fees heard about a scientist who was using computers to track weather

conditions and pollutants. was it possible that science could re-create the weather condition on the day of the accident? ññññ (announcer) every woman has many sides

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the accident from the knoxville and chattanooga airports, as well as from two nuclear power plants -- one only 18 miles from the scene. weather records indicated that there were few, if any, clouds on the morning of the accident. winds were light, and the temperature dropped rapidly the night before from a high of 60 degrees in the afternoon to almost freezing. this 30-degree drop in temperature could cause a weather phenomenon called an inversion. an inversion occurs when the temperature on the ground is cooler than the temperature in the atmosphere. this prevents air and moisture from dissipating into the atmosphere, pushing the moisture back towards the ground. very early on the morning of the accident, a helicopter pilot flying over interstate 75 noticed a mushroom-shaped cloud, similar to this one, over the bowater paper mill smokestacks, three miles east of the accident

site. eschenroeder believes this was visual confirmation of the inversion. water vapor is produced naturally coming from evaporation from lakes, streams, rivers, and ground moisture. dr. eschenroeder calculated that the evaporation rate of the natural bodies of water in the area was only 392 gallons per day. this was barely enough to create even a light fog, let alone the dense, thick fog described by accident victims and rescue personnel. eschenroeder was convinced there had to be another source of water vapor which caused the thick fog. he noticed a series of ponds which straddled the interstate highway on two sides. these were wastewater treatment ponds, which belonged to the bowater paper plant. these ponds were used to clean the industrial wastewater from the paper mill. in two of the ponds, aerator fans would propel the water up

into the air. most of the water dropped back into the ponds. some of it did not. >> that's called "drift." drift droplets are things that drift away from the site of where they are formed. all the other droplets fall back to earth or fall back to the pond where they originate. so we had to do some original calculations in an engineering-estimate fashion for emission of those droplets. >> narrator: eschenroeder calculated that these wastewater treatment ponds added 10 million gallons of water vapor into the atmosphere in the 24 hours preceding the accident -- far more than the 392 gallons from the natural bodies of water. at the paper plant itself, an additional 1.5 million gallons of water vapor was being released each day from the smokestacks. but it wasn't just water vapor that was being released from these smokestacks. paper plants release what are called "particulants" as waste

from the paper-production process. particulants are microscopic particles which become surfaces on which water vapor can condense, and this leads to fog. >> you not only had the fog potential from the presence of the water vapor, but you had a place for it to form in the surfaces of these microparticles -- these condensation nuclei. >> narrator: but how could eschenroeder tell if the water vapor from the bowater paper plant three miles away caused the fog on the interstate highway on the day of the accident? he found part of the answer on this aerial videotape shot by a local videographer a few hours after the accident. eschenroeder recognized the wind pattern as a drainage flow, which carries cooler air down into the valley. but eschenroeder needed to know in which direction the drainage flow was heading. to do that, he needed to know the exact position of the airplane.

using navigational charts calculating the position of the sun from the glint angle off the wing and ground references, he identified the plane's position relative to the paper mill and the accident site. the videotape convinced eschenroeder that the drainage-flow wind pattern was headed west -- from the location of the paper mill towards the accident site. >> as to the cause of that accident that day, there's no doubt in my mind that the industrial fog created by water emissions from that bowater paper mill was the preponderately major factor in forming the fog that caused the accident. >> narrator: attorney doug fees now had scientific evidence and proceeded with the civil suit he filed earlier against the bowater paper company and the state of tennessee. we can't lin a bubble.

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>> narrator: as mike curtis drove onto interstate 75 on the morning of the accident, the sun was so strong, he took his jacket off in the car. when curtis approached the fog zone, the fog-warning lights in one direction weren't working. and those in the other direction had been blinking continuously for three days and were ignored. the daily police fog patrols had been abandoned years earlier. once in the thick fog, visibility was near zero. mike curtis never saw what he hit. curtis heard crashes, people crying for help, the explosions. >> i knelt down and asked god to help me... to get through it. >> narrator: he helped a young boy caught inside a motor home. >> 12- or 13-year-old boy that i got out. his mother was inside screaming. the adrenaline was pumping, and i ripped the window out and got

her out. >> narrator: after saving the boy and his mother, curtis tried to save the father, but he burned to death. there was also tragedy for a woman driving with her granddaughter. this is all that was left of the car. >> this car was smashed completely flat like an accordion. >> the car was compacted down to something in the neighborhood of 30 inches long. by some miracle this little girl lived through the entire thing. >> narrator: the grandmother died. randall mckeehan and his two children also suffered a loss that day. they lost a wife and mother when judith mckeehan burned to death in the accident. >> there was no body. she was over 90% gone. it was like she had been cremated. and there wasn't nothing to view. she still had remains, ashes, which i'm not saying could be

identified, but still knowing that she died in that vehicle, i did the best i could to get everything of all her ashes out. and i spread them across that field right out there. and, uh... i just... i guess that was, uh... the only thing i knew to do. >> narrator: doug fees' case was set for trial in 1994, more than three years after the accident. bowater disagreed with the scientific calculations used in the eschenroeder study and hired its own scientific expert. dr. george mcvehil is a meteorologist from denver. his study concluded that bowater's contribution to the fog on the day of the accident

was less than 1%. >> our conclusion was that the fog formed by a natural process due to mixing of moist air at different altitudes at about 9:00 on the morning of december 11th, after the sun had come up and heated the ground enough to start the mixing process. that, in a very abbreviated and simplified form, is what caused the fog on that morning. >> narrator: but shortly before the trial, the courts ordered bowater to release a study it commissioned in 1979 from its own consulting firm, environmental research & technology. in it, ert states that... doug fees never got the chance to prove his case in court.

before the trial, the state of tennessee reached an out-of-court settlement with fees on behalf of the families he represented. because of the malfunctioning fog-warning system, the state settled for $800,000 and also agreed to install a $4 million computerized fog-detection system. when the fog reaches a certain density, large signs automatically notify drivers of fog in the area and sensors trigger gates on key entrance ramps, closing access to the highway. bowater also settled out of court with 30 victims and families represented by doug fees and other attorneys for $11 million. bowater continues to maintain that the paper mill and treatment ponds had nothing to do with the fog on the day of the accident. however, bowater agreed to limit its use of treatment pond number four, which sits near the

highway. >> but the issue isn't whether or not pond four is a contributor to fog, whether natural water conditions that are in the community are contributors to fog. the real point is that fog exists in that particular place from time to time. it's natural fog. and the traffic-control mechanisms in the highway have to be sufficient to warn motorists. >> narrator: despite the settlement and the new fog-warning system, many still believe the highway is unsafe. >> warnings are never the answer when you can do better. closure of pond four is not enough to solve the problem. the chance of this happening again has been substantially reduced, but the risk has not been eliminated, nor has the hazard been eliminated. >> this is only the third time

i've been here. any officer will tell you that this is, to me -- it's a memorial site. that bridge is a memorial because a lot of people died because a lot of people died here -- needlessly. >> narrator: for more than a year, angry, hateful letters were sent to a first-grade schoolteacher in a small mountain village in pennsylvania. many were sexual in nature. some threatened violence. when scientists analyzed the letters, they found evidence that the stalker knew a lot about the victim -- more than anyone could possibly imagine.

in 1993, some hate mail began to arrive at the coolbaugh learning center, a public elementary school in the pocono mountains in eastern pennsylvania. the letters were unsigned and sent to the principal, making serious allegations against a first-grade reading teacher, joanne chambers. she had been teaching in the school district for the past eight years. >> i thought it was just somebody, a disgruntled employee. i just wanted to know who it was, and i thought it was a

thing that you could sit down with that person and talk it out and fix it. >> narrator: soon, letters were sent to joanne chambers herself at both home and at school. joanne chambers was popular with students and was an unlikely target of a hate campaign. she was married with a 10-year-old son and had no known enemies. >> i can speak with assurance about joanne's teaching abilities. she's highly recommended by other teachers in the district. she was also highly respected by parents. she was an outstanding teacher. all her recommendations show that. >> narrator: it appeared that someone had a grudge against her. chambers found the whiskey bottle in her desk drawer and

said personal items were missing. >> there were things missing from my drawers. the picture of my child and myself and my friend and her daughter was taken from my desk. >> narrator: the police suspected that a fellow teacher or school employee was sending the letters, since they often alluded to activities going on inside the school. one of the letters contained an interesting clue. it was a snide reference to the school's superintendent as "colonel klink," a character in the "hogan's heroes" television series. a teacher in the school was once overheard referring to the superintendent in this way. her name was paula nawrocki. like joanne chambers, nawrocki also taught first grade and had worked in the school district for 18 years. >> i was totally surprised. i was positive that it wasn't anybody in the building, that it could be explained in some other

way. >> narrator: the letters continued. but soon there were other incidents. the first was something joanne chambers found under her desk. >> i went to start my lesson with my children and sat down on a chair and had a dress on and put my hand underneath to straighten the dress out, and it was covered with feces. and... i couldn't even tell you what i felt like. i felt sick to my stomach. it was like it was not happening. it was like, this could not happen. >> narrator: just a few days later, a hidden camera captured several teachers entering joanne chambers' vacant classroom. one removed chambers' coffee cup from her desk. it was paula nawrocki. the photograph of joanne chambers stolen from her desk was pasted onto a nude

picture, photocopied, and distributed throughout the schoolyard, mailed to parents' homes, and a copy was taped to the door of a local store. >> there were phone calls to parents, saying that i was a lesbian, that i had aids, that i shouldn't be teaching their children. >> narrator: the fbi suggested that joanne chambers be given a lie-detector test to validate her various claims. paula nawrocki also volunteered to take a lie-detector test, hoping to clear her name after suspicions arose from the colonel klink reference and the coffee-cup incident. one of the two failed on the most crucial question of all. depression is a serious medical condition that can take so much out of you. i feel like i have to wind myself up

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>> narrator: after 10 months of threatening letters, x-rated pictures, and hidden video surveillance, police believed they had a break in the stalking case. joanne chambers and paula nawrocki both took lie-detector tests about their knowledge of the threatening letters. each was asked whether they were involved in making or sending any of the harassing letters. one passed. the other failed.

>> i was told that i failed my polygraph. >> narrator: paula nawrocki became the primary suspect. >> i was very upset. i couldn't believe that it was making things worse instead of better. >> narrator: nawrocki said she was videotaped taking joanne chambers' coffee cup because chambers had asked paula to get it for her. the surveillance videotape shows that joanne chambers and paula nawrocki were both in the classroom and left together just moments before paula returned for the coffee cup. police asked nawrocki if they could search her home. and once again she voluntarily complied. >> they took with them an old typewriter that we had. they took different kinds of paper and different envelopes. >> narrator: the analysis of nawrocki's typewriter revealed that it was not the one used to type the threatening letters. the paper and envelopes from

nawrocki's home did not match those used in the threatening letters, either. nawrocki's reputation as a by-the-book teacher and strict disciplinarian was in sharp contrast to joanne chambers' loose and fun-loving classroom style. >> the way the police saw it, paula was jealous of joanne chambers' unconventional teaching style and the popularity that she gained from that style. paula nawrocki was more of a by-the-book, conservative teacher who favored traditional teaching methods, whereas joanne chambers would show up in the classroom wearing jeans and a mickey mouse t-shirt, and she would do things like stage water fights with the school administrators, which the police believe angered paula nawrocki. >> narrator: as the investigation continued, so did the threatening letters. >> letters went out to parents saying that i was molesting their children. i thought my career was gone. i thought i was gonna be in jail. i didn't know what was gonna happen.

>> narrator: by the fall of 1994, the letters included death threats. for her own protection, joanne chambers was transferred to another school. shortly after her transfer, a box in pink wrapping paper was found at the front door of the school. inside was a barbie doll, the throat slashed with a razor blade and covered with paint the color of blood. the dress was identical to one often worn by joanne chambers. the hair was cut and styled like chambers' as well. >> i said goodbye to my husband. like, i wanted him to remember me saying goodbye. i lived every day thinking that it was truly possible that it could be my last. >> narrator: in november of 1994, chambers said a car tried

to run her off the highway. she said she saw the face of the driver. >> i go off the road. i pull over. i look. she's looking right at me. i will never forget that look. never -- i will never forget it. she looked right at me. >> narrator: she said the face she saw was a face she knew. io tried activia?

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denied the allegation but was arrested and charged with harassment, stalking, simple and aggravated assault, making terroristic threats, and recklessly endangering the life of joanne chambers -- over 100 counts in all. >> i was finding out that i was charged with many, many horrendous things i had never heard about before. >> narrator: the school district suspended her from her teaching position with pay. if convicted, she could serve five years in jail. after nawrocki's arrest, the letters, threats, and mailings stopped. nawrocki maintained her innocence and hired both an attorney and private investigator to help. the investigator was a former state policeman, and even he admitted that paula's situation did not look good. >> my first thought was, well, she's probably guilty. it just looked overwhelming when you looked at the whole complaint. >> narrator: the fbi found some

partial fingerprints on the threatening letters, but they did not match paula nawrocki's. the defense team wanted to see if any dna was present on the threatening letters. the prosecutor would allow dna testing by the defense only if the results were fully disclosed, regardless of the outcome. paula's defense team wanted to make sure she understood the ramifications of such an agreement. >> he asked, "would there be any possible reason that any of my dna should be on any of it? any possibility whatsoever?" and i said, "no." >> "paula, if we do this testing, and your dna is found on these stamps or envelope flaps, you're going to jail." >> narrator: the cost of the dna testing, approximately $7,000, would have to be paid by paula nawrocki. blood samples from both paula and her husband were sent to a

local dna lab, along with the threatening letters and the envelopes. >> the amount of dna that would wind up on the back of a stamp or an envelope flap depends on how hard you lick the envelope, how much cells that you shed from the inside of your mouth. there are variables, so it's hard to predict exactly what the value would be. but it is there. in some cases there's more dna than others. >> narrator: first, scientists use steam to gently remove the stamps from the envelopes. the back of each stamp and envelope flap was swabbed for epithelial cells, which come from saliva. dna was found on the back of one set of stamps and on one envelope flap. the number of cells recovered was so small that forensic scientists performed a process called "polymerase chain reaction," or pcr, which amplifies or copies the dna in those few cells to make enough for testing.

>> what we're looking for to see is how does this dna that we've extracted compare to somebody else's dna? now if the dna is from a similar source, you'll get the same pattern of blue dots on a white strip. >> narrator: this is the genetic profile of the individual who licked the stamps. when the dna profile of paula nawrocki and her husband were compared to the dna from the back of the stamps, there was no match. >> for example, paula nawrocki has two dots here, and the dna from the back of the postage stamp only has one. so, therefore, right away we can exclude paula nawrocki with just this one genetic marker. we looked at five different genetic markers, and four out of five can exclude paula nawrocki. >> dna was found, and it did not match paula, and it did not match len nawrocki. which meant that someone licked

those stamps, and it wasn't len or paula. >> we thought it was gonna blow apart the whole case. we thought we were done. >> narrator: now armed with the dna profile of the stalker, the manhunt had just begun. %%%%%%%%%%%%%%%%

>> narrator: when dna testing of the stamps and envelope flap did not match paula nawrocki or her husband, the defense team went one step further. they wanted to find the individual whose dna was on the threatening letters. >> if paula didn't do it, there was only one other person that could have done it, because there's only one other person that knew the circumstances of all these letters, that knew everything that was going on. that was joanne chambers. >> narrator: was it possible that the alleged victim wrote the threatening letters and mailed them to herself?

the defense uncovered some information which pointed in that very direction. police in the neighboring town of carbondale, pennsylvania, told defense investigators that chambers had a history of reporting suspicious incidents, from burglaries to fires. >> they said every crime that she's been a victim of has some weirdness attached to it. and just off the top of their heads, they started relating different crimes that supposedly she's been a victim of. >> narrator: when anderson researched chambers' employment history, he learned that chambers reported similar threatening letters and also reported finding feces on her classroom chair while in another school district years earlier. to find out if it was joanne chambers' dna on the threatening letters, jim anderson needed her dna

profile. for that, he looked in her trash. once trash is placed at the curbside, the owner gives up all legal rights to what's inside. >> one plastic drinking straw. one used -- it looks like toilet tissue. >> narrator: plastic straws, used tissues, and a cotton swab with earwax -- all items with possible genetic material were sent to the dna lab for testing. dr. lichtenwalner identified two different dna profiles from the mucus, saliva, and earwax samples from the chambers' trash. >> the dna from one of the household members was similar to the dna on the back of the stamps and the envelope. >> narrator: with these dna results, the defense team demanded that all charges against paula nawrocki be dropped. the prosecution refused, and joanne chambers provided a blood sample for further dna testing.

once again, joanne chambers' blood dna matched the dna from the stamps and the envelope flap. >> you can see how all five genetic markers line up perfectly between the dna of joanne chambers and the dna from the back of the postage stamps. >> narrator: the odds of someone in the random u.s. population having the same combination of five genotypes tested was one in 14,925. >> the match was fairly significant in that that's a small community there. so it's unlikely that too many people are gonna be walking around with a similar dna pattern. >> narrator: despite the second dna test, the prosecution refused, once again, to drop their case against paula nawrocki. during the trial, the prosecution presented the circumstantial evidence against paula nawrocki, including the coffee-cup incident and the

"colonel klink" reference in one of the threatening letters. for the defense, teachers from joanne chambers' former school district testified that she made similar claims of harassment years earlier. but it was the dna evidence that stunned most courtroom observers. >> the dna was definitely the bombshell. to hear that joanne chambers' saliva was found on the stamps of one of the threatening letters and the flap of another envelope -- it was just unbelievable. >> narrator: but on the witness stand, under oath, joanne chambers had an explanation. she said the prosecutor left her alone with the evidence, and the stamps fell off one of the envelopes. she said she licked the stamps to reattach them, and when that didn't work, used a glue stick. >> at the very least, she showed poor judgment. and at the most, she tampered

with important evidence. >> narrator: dr. lichtenwalner testified that she saw no glue-stick residue on the stamps when she removed them for dna testing. as a lifelong stamp collector, she has experience distinguishing glue-stick residue from regular stamp adhesive. >> i know gum from knowing stamps, and it looked to me just like the gum on recent u.s. stamps. and it's smooth and glistening, and it looked just like that. there was no outward evidence that a glue stick had been used. >> narrator: the trial lasted five days, and it took the jury less than two hours to reach a verdict. they found paula nawrocki not guilty. >> reaction after the verdict was the most amazing thing i've ever seen. the alleged victim was being treated as the defendant, and the defendant was being treated as the victim. in the hallway, jurors sought out paula nawrocki and hugged her and told her how much they

loved her, while joanne chambers left the courthouse virtually ignored. >> narrator: joanne chambers denies that she created the campaign of threats against her. >> i could never, ever do this stuff to myself. i don't think that i could be functioning in a world as a parent, as a teacher, as a wife if i were that sick to do that to myself. >> i think joanne chambers did it to herself, yes. i think she sent the barbie doll. i think this was all a stage for joanne. >> i hope the lesson that people can learn from this is that you really are supposed to be innocent until proven guilty, and you aren't supposed to be guilty until proven innocent. >> i've never seen anything like this, and if i cover cases for another 40 years, i think i'll give you that same answer still.