embalmed tissue. one of the many scientific forensic advances that occur almost daily on a warm summer evening in 1980, a young married couple took their horses out for a leisurely ride through the woods. one of the horses bucked, and threw the rider. the autopsy confirmed it was an accident. but the family wasn't so sure. hillsdale county, michigan, population just over 40,000. this is farm country. soybeans and corn mostly. a hospitable place where friends drop in unexpectedly, and there's always room for one more at the dinner table.

25-year-old shannon mohr was a quiet, unassuming young woman who grew up in nearby toledo, ohio. >> she was a very good student in school. and she said when she was in first grade, because she went to catholic school, i'll be a nun or i'll be a nurse. and she became a nurse. >> in september of 1979, shannon mohr met an eligible bachelor from hillsdale county. 36-year-old david davis. the two met at a friend's wedding. >> shannon said, mom, i met this real nice man. and he told me he was a millionaire. he has farms all over the united states and in belize. >> i thought the world of him from the very beginning. he was just a kind of a rugged outdoor type person. liked to fish and hunt. i thought he was good to my daughter. and that's the only thing that i cared about. >> and i said to her, shannon,

if you let this one get away from you, you're nuts. >> after an eight-week courtship, shannon and david married and moved to david's michigan farm. it seemed to be the ideal place to raise a family. they bought two tennessee walking horses which were recommended because of their gentle nature. on july 23rd, 1980, ten months after the wedding, shannon and david rode their horses to see their neighbor, dick britton. dick was having a problem with some farm machinery, so david spent time helping him. >> we worked probably half an hour on this tool, and shannon come up and asked me about taking our boy norman home with them. and i went to turn around and tell her, sure, go ahead and take him, and dave said, no, you can come get him in the morning. shannon had asked me the question, but he had answered. and so i dropped it.

>> david and shannon then mounted their horses and left. instead of going back the way they came, they took a short cut through the woods. a short time later, david raced out of the woods back to dick britton's farm. >> dick, come quick! >> he come riding back and he had blood on his shirt. he was sweaty, perspiring hard like he had been in a fight or something. kind of half fell off his horse and said that shannon had fell off her horse and she was hurt bad. >> david said that shannon's horse had bolted. he said she fell and hit her head on a rock. shannon was lying on her back. her eyes were closed. there was blood on the back of her head. shannon's blouse was undone. and her sneakers were off, which britton thought was unusual. shannon was rushed to the nearest hospital. >> i was blowing the horn, tooting it as loud as i could.

this nurse come running out. and i says, we need a doctor. i said, i'll run to the front and tell them. she's hurt bad. >> shannon's lifeless body was wheeled into the emergency room where doctors checked for vital signs. there weren't any. the time of death was arbitrarily set at 8:45 p.m. the wound in the back of shannon's head and the x-rays taken at the hospital were consistent with david's explanation that she had fallen from her horse and hit her head. her death certificate listed the cause of death as multiple cranial and cervical spine injuries. since shannon died in one county and was declared dead in another, no autopsy was performed because of a jurisdictional mix-up. that failure would later come back to haunt shannon's family. [ hoof beats ]

i wish... please, please, please, please, please. [ male announcer ] the wish we wish above all...is health. so we quit selling cigarettes in our cvs pharmacies. expanded minuteclinic, for walk-in medical care. and created programs that encourage people to take their medications regularly. introducing cvs health. a new purpose. a new promise... to help all those wishes come true. cvs health. because health is everything. cvs health. thanks for tnorfolk!around and i just wanted to say, geico is proud to have served the military for over 75 years! roger that. captain's waiting to give you a tour of the wisconsin now. could've parked a little bit closer... it's gonna be dark by the time i get there. geico. proudly serving the military for over 75 years.

shannon mohr had two life-long dreams. the first, to become a nurse.

the other, to raise a family. she graduated from nursing school and had been married less than a year. her dreams for a family would never be fulfilled, because of a freak horseback riding accident which took her life at 26. when shannon's parents, lucille and bob mohr, arrived at the hospital, her husband, david davis, was in the hall crying. they all instinctively hugged each other, just as they always did. >> he grabbed me. and as he grabbed me, he ran his hand under my face, and i looked and there was three deep scratches. and i mean deep scratches. >> shannon's father had other concerns. david insisted that shannon's body be cremated. as a catholic, bob mohr was opposed. the mohr family wanted to take shannon's body back to ohio to bury her there. at that point dick britton stepped in.

>> her mother was crying. and bob was crying. so i stood right up and yelled at him and said, dave, that's her folks. nobody knows her out here. let them take her back to toledo and bury her there. people will come to her grave and put flowers on it. she don't know anybody here. and he backed down and said okay. >> the next day, deputies from the hillsdale county sheriff's department visited the scene of the accident. they found the bloody rock. the only rock for some distance around. not far away were shannon's untied sneakers lying about five feet apart. and there was an area where the grass had been matted down. >> they looked around a little bit, took a few pictures, and left. and i asked them about the shoes, and they said, no, you can have them. >> over the next several days, the mohrs made arrangements to bury their daughter. david's parents, whom the mohrs

had never met, came to the funeral. and what they had to say made it clear that everything david had told the mohrs about his past was a lie. he was not a millionaire. he didn't own farms all over the country. and even more shocking was the fact that he had been married before and had two daughters. the mohrs believed their daughter's death was no accident. dick britton had come to the same conclusion, because of something davis had said the day after shannon's death. >> so the next morning we're sitting at my table and he wants to know about the neighbor. he said, does the neighbor still want to sell his farm? and i said, huh? and he said, never mind. and i'm thinking, how can you be thinking of buying a farm the next morning after your wife died. >> a week after shannon's death, dick britton and the mohrs took their suspicions to the hillsdale county sheriff's

office. the mohrs discovered that davis had taken out insurance policies on shannon's life totaling $330,000 during the ten months they were married. the mohrs demanded an autopsy, and shannon's body was exhumed a month after her death. the autopsy revealed a 3 1/4 inch gash on the back of shannon's head along with bruises on her upper back, left shoulder, her upper right arm, reason, and left cheekbone. -- right hand, and left cheekbone. but they found no evidence of foul play. the coroner concluded that shannon had died of the head injury. the sheriff's department considered the case closed. >> believe it or not, yes, when they first brought her up and said there was no evidence, i thought, they're missing something.

there has to be. and i knew then we had to keep going, one way or another, because something was wrong. >> the mohrs weren't the only ones who were suspicious. billy bowles, a reporter for the "detroit free press," uncovered some devastating information on david davis, painting him as a consummate liar who lived off money gained from suspicious insurance claims. one claim was for a questionable fire on a farm davis once owned. >> the vacant farmhouse burned, and he collected about $30,000 insurance for that. the barn burned mysteriously while he was away, and he collected $6,000 for that. in addition to those, he had left a job at chrysler after a very suspicious injury. and he was collecting workmen's

compensation and social security for that. >> bowles' investigation revealed, among other things, that davis had studied pharmacology in college. armed with this new information, the mohr family asked the state's attorney general to open a new investigation. shannon's autopsy revealed she died of a single blow to her head. detective don brooks had two theories. >> number one, this young lady actually fell from a horse and struck the only rock around squarely and it really is an accident or, number two, he killed her. the only way, in my opinion, for him to get her in a position where he could slam her head into that rock was to have her completely immobilized. so we wanted to look at the possibility that she was drugged at the time. something that would paralyze her, but leave her heart still pumping and still -- she's still alive.

>> with davis' background in pharmacology, police asked local veterinarians what drugs farmers use with their animals that can cause paralysis. one of the drugs mentioned was a powerful muscle relaxant named succinylcholine used in animal surgery. it's also used in humans. in large doses, succinylcholine can be fatal. but there was a problem. succinylcholine is broken down in the body almost immediately, and is, therefore, undetectable. if this was the drug david davis used on shannon, he had gotten away with murder. just take a closer look. it works how you want to work. with a fidelity investment professional... or managing your investments on your own.

helping you find new ways to plan for retirement. and save on taxes where you can. so you can invest in the life that you want today. tap into the full power of your fidelity greenline. call or come in today for a free one-on-one review. i have the worst cold with this runni better take something. dayquill cold and flu doesn't treat your runny nose. seriously? alka-seltzer plus cold and cough fights your worst cold symptoms plus your runny nose. oh, what a relief it is. i am a lot of things. i am his guardian. i am his voice. so i asked about adding once-daily namenda xr® to his current treatment for moderate to severe alzheimer's. it works differently. when added to another alzheimer's treatment, like aricept®, it may improve overall function... and cognition. and may slow the worsening of symptoms for a while. (man) namenda xr doesn't change how the disease progresses.

it shouldn't be taken by anyone allergic to memantine, or who's had a bad reaction to namenda xr or its ingredients. before starting treatment, tell their doctor if they have, or ever had a seizure disorder difficulty passing urine, liver, kidney, or bladder problems, and about medications they're taking. certain medications, changes in diet, or medical conditions may affect the amount of namenda xr in the body... and may increase side effects. the most common side effects... are headache, diarrhea, and dizziness. (woman) all my life, he's protected me. now i am giving back. ask their doctor about adding... once-daily namenda xr. mayo? corn dogs? you are so outta here! aah! [ female announcer ] the complete balanced nutrition of great-tasting ensure. 24 vitamins and minerals, antioxidants, and 9 grams of protein. [ bottle ] ensure®. nutrition in charge™.

in the seven months since shannon mohr's death, her husband, david davis, sold his michigan farm and moved to the bahamas where he lived on his sailboat with his new girlfriend. davis was waiting for the conclusion of shannon's investigation so that he could collect the $330,000 from her life insurance policies. although the autopsy was consistent with davis' version

of her death, the crime scene wasn't. davis said he and shannon were riding back to their farm when shannon's horse bucked, threw her to the ground, and her head hit a rock. but the rock she hit was the only one within 100 yards. for some unexplained reason, shannon's blouse was unbuttoned and her shoes were removed and placed a few yards away. the grass was matted around the body. police wondered whether davis might have injected shannon with some kind of paralyzing agent like succinylcholine before her death. there was no known test to identify succinylcholine. but local scientists heard about a new test developed in sweden which was having some success finding succinylcholine, even in embalmed tissue. two doctors took the tissues to the carolinska institute in sweden.

it took a team of toxicologists several weeks of trial and error just to extract a sample they could test. >> we were working ten-hour days. we were working on trying to get the method perfected. once we got the method perfected, then we started analyzing all of shannon's tissues. >> the tests were conducted with a mass spectrometer which bombards chemical molecules with ions, shattering them into their molecular components. the fragmentation creates a chemical fingerprint that can be prepared to other chemical fingerprints to determine the unknown's identity. after weeks of testing and hundreds of tests, scientists finally got a break. >> i looked over at one corner. and in that one corner was one piece of paper. and on that piece of paper was a perfect mass spectra for succinylcholine. and that piece of paper was identified to have come from

shannon's tissues. >> when prosecutors in michigan learned the news, they were elated but they didn't feel it was enough. they wanted more evidence and needed to know where davis had injected her. as a result, for the second time, shannon's body was exhumed. >> the vast majority of the injuries sustained by shannon were on the left side of her body. her left shoulder. her left back and the left side of her head. which would indicate a fall to the left and then falling on your left. on her right side, however, there was a bruise in the upper quadrant of the right arm and also on the hand. >> dr. forney took tissue samples from all the bruise sites and returned to sweden.

he discovered that shannon's right wrist and upper arm had much higher concentrations of succinylcholine than her other tissues, an indication that davis had injected her twice. based on that evidence, david davis was finally charged with shannon moore's murder. when police went to arrest davis, he was nowhere to be found. the search for davis dragged on for months and then years. you know.... there's a more enjoyable way to get your fiber. try phillips fiber good gummies. they're delicious and an excellent source of fiber to help support regularity. mmmm. these are good!

the tasty side of fiber. from phillips

police believe that david richard davis murdered his wife by injecting her with a lethal drug making the death look like a horseback riding accident. the drug he allegedly used was believed to be undetectable. but a team of determined toxicologists found it. for 8 1/2 years, davis eluded police before they finally got a break. a story about shannon's murder appeared on network television. an old girlfriend of davis' called police with a tip. >> she called and she wanted to tell me about an individual that she thought could be david davis. she knew him by a different

name. however, she was very reluctant to get involved. she was in fear of her own life. >> the caller revealed that davis was living in american samoa with a samoan wife under the name david meyer bell. in the eight years since shannon's death he had lived in california, alaska and hawaii. the fbi arrested davis and he returned to michigan for trial. >> we know that he courted and dated several women before shannon and asked each of them to marry him in an extremely short period of time, something like 14 months he asked five different women to marry him. the first one who said yes became his victim. >> blumer said the motive was money and that the murder was premeditated. prosecutors believe that after the couple left dick britton's farm, davis coaxed shannon off her horse under the pretext of having sex.

the couple had a habit of making love outdoors. as shannon took off her shoes and unbuttoned her blouse, prosecutors believe davis snuck up behind her and injected the succinylcholine in the shoulder. the injection didn't take effect immediately. the two fought, matting down the grass. he then hit shannon on the head with the rock and injected her again. this time, in the wrist. the dose killed her instantly. >> if you were given an injection of succinylcholine outside the hospital where they can help you breathe with a respirator, you'll die of suffocation. that's exactly what happened to shannon davis. i believe that the succinylcholine answered the ever-present question in the jury's mind which is if she didn't die from being thrown off a horse, then what killed her?

>> the jury deliberated for 2 1/2 hours. >> my heart was pounding so hard. and i thought, it's over. we've got him. >> david davis was found guilty of first-degree murder. >> i remember the courtroom, which was full, burst in applause. and instead of standing around and shaking hands, i had to leave. i had to leave the courtroom. there's a law library right off the courtroom. i had to go in there. and it was pretty emotional. >> he was sentenced to life in prison. >> i know we went out to the cemetery right afterwards and we looked down and said, we got him. he was that good of a liar that i shouldn't feel too bad that he fooled us. but i think of her living with a killer all that time, ten

months, and i didn't know it. and i also think i should have picked something out and i didn't. the surf and sand of central florida make this a popular vacation spot. but the area lost some of its luster in 1995, when a serial killer set up shop. after the fourth body was discovered, police knew an important detail about the killer. he had an unusual dog with an unusual drug habit. tampa, florida, is known not only as a tourist destination but it also has more thunderstorms than any other location in the united states. the name, tampa, is derived fr