he wanted to own divas when he walked in there. and he is just a small little man and perhaps the most incompetent killer that bucks county's ever seen. up next, a violent thunderstorm provides cover for a brutal murder. >> an absolutely brutal crime scene. >> obviously, this was a case of an overkill. >> there are plenty of suspects with clear motives, but they all pass polygraph tests. >> it's not 100% reliable. >> if investigators didn't find the one tiny clue left at the scene, they might never have solved it. the real estate development business in texas always seems to be active. darrell north, a manager for a multibillion dollar development company, had no shortage of

work. >> darrell north was in charge of building budget suites for a company out of las vegas, and he had been in charge of building several in this area. >> darrell had a reputation as a fair-minded boss who set high standards. >> i asked a subcontractor, was darrell hard to work for? was he mean? and he said, no, he was not. he said he expected quality work. >> i've seen dad fire numerous subcontractors over the years. my dad had the ability to get his point across very clearly. he was very pointed. he was very direct. >> darrell was always punctual. so when he didn't come home from work one day and didn't answer his phone, his family was concerned. >> when i got to the job site, it was after 11:00 at night. the lights of his trailer were

on. and his car was out front, and i knew his car hadn't been moved because it was dry underneath his vehicle when everything else was just drenched. >> the door was padlocked. his son knocked on the door, but got no answer. >> i climbed up on the rail with a flashlight trying to shine the flashlight into that dark office to see if dad had a heart attack or something had happened. >> mark saw his father on the floor. >> i saw dad laying against the door. and he was just laying face down, you know, not moving. >> paramedics and police declared darrell north dead at the scene. he'd been stabbed repeatedly. blood was spattered everywhere. >> it was an absolutely brutal crime scene, as would be typical with any case where there's multiple stab wounds. there was a tremendous amount of blood. >> there was blood in two of the three rooms.

it was obvious a life and death struggle had taken place. >> there was also a hole punch that was discovered in close proximity to mr. north's body that was bent. that would lead me or any other investigator to believe that either mr. north may have been struck with that hole punch or mr. north may have struck his assailant with that hole punch. >> there was a trail of blood from the filing cabinet to darrell's body. then, to a desk. on top, police found a machete, the type used to clear brush from construction sites. it was perfectly clean. >> it actually wasn't blood-soaked, but we didn't know if it might have been used and then cleaned off and placed there. >> darrell north's secretary told police there were normally two machetes in the trailer. >> there was a second machete that had gone missing. >> police assumed this was the one used in the attack.

>> the extra wounds on the back of the head, which almost decapitated him, indicated a tremendous desire to make sure that the person was deceased. >> darrell's wallet was still in his pocket. nothing had been stolen. there was no sign of forced entry. this and the level of violence indicated a very personal crime. >> out of the 40 cases that i've worked, this was the only one that had that type of rage exhibited. >> darrell hired many contractors, so his decisions could either make or break some of them. someone's anger had spiraled out of control. but police and darrell's family had no idea who it was.

darrell north's autopsy revealed he'd been stabbed 46 times with two different weapons. a clear case of overkill. >> overkill, as we define it, is wounding a person way beyond what would be required to kill a

person. so we frequently see not just a few wounds, but many, and all indicative of rage that is going on between the two involved in the assault, the victim and the assailant. >> a machete missing from his office was believed to be one of the murder weapons. the other was believed to be a knife. >> a single sharp agent, a blood agent. we could predict that it was a larger knife. some of the wounds were at least an inch, inch and a half in width on the body surface. >> the family tried to help investigators by identifying anyone who might have had a reason to harm darrell. >> i thought it must be a stranger, you know, that maybe was robbing him or something. i could not, in my wildest imagination, you know, believe that someone would do that.

>> darrell's secretary told police that everyone left the construction site early on the day of the murder because of the severe rainstorm. she said darrell stayed behind to meet with a contractor named curtis pope. >> curtis pope was a pool contractor. darrell was basically mentoring curtis into the construction business. and he stayed approximately 20, 25 minutes. he left darrell. darrell said he was going to wait out the rain and let the traffic die down before he headed home. >> darrell's wife told police curtis pope could not be the killer. >> curtis pope had done some repair work on our pool. i said, please don't spend your time looking at curtis pope. he did not kill darrell. please, you know, spend your

time looking for the person that did. >> pope was distraught over darrell's murder. >> he came through the receiving line crying, and i thought he was so touched by darrell's death. and he said, i loved darrell. he was better to me than my own father. >> pope was 40 years old, married, with a young daughter. he did, however, have a police record consisting of arrests for petty theft. since he was the last known person to see darrell alive, he was automatically considered a suspect. pope agreed to take a polygraph examination and passed. >> it is not likely that somebody could come in and intentionally be untruthful and still pass the polygraph test. >> the next suspect was bob johnson, a roofing contractor. darrell fired johnson just two weeks before his murder. >> he was upset that he wasn't

going to continue to work there because, according to him, darrell had promised him continued work. >> darrell's family never met johnson, but they'd heard of him. >> darrell had mentioned that he had had some problems with him. he usually didn't bring his problems home, and so since it was something that he had shared with me, i thought it was probably serious. >> incredibly, just two days after darrell's murder, johnson called asking to get his job back. >> the superintendent felt like it was odd that bob johnson was calling there, when can i come to work, after the fact, after darrell's been murdered, because his belief was that darrell didn't want him there. >> johnson said that on the day of the murder he was with his child in a dallas hospital. this was verified. but he still had time to commit the murder.

>> the alibi wasn't sufficient enough, in my mind, to totally exclude him. >> but like curtis pope, he, too, passed a polygraph examination. >> the polygraph is just a tool. it's not 100% reliable. that's why it's not admissible in court. >> if it hadn't have rained, maybe we could have gotten fingerprints. but you can't focus on what you could have had. you got to find what you do have. >> investigators needed forensic evidence to solve this crime and hoped to find some of it at the scene. every day, people fall. from a simple misstep, to tripping over a rug, to just losing their balance. and not being able to get up from a fall can have serious, lifetime consequences. being prepared is important. philips lifeline with autoalert is more than just a medical alert button. it's an advanced fall detection system designed to get you help quickly. if you fall and you're unable to push your button, the fall detection technology within autoalert can trigger the button to automatically place a call for help.

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darrell north's murder was so violent that forensic tests were needed to make sense of what happened. >> we had numerous types of blood stains. they included passive blood drops. we had smears, transfers, and frankly, there was so much blood, that you would be hard pressed to try to classify some of it as to how it got there. >> we took many samples. we took 23 samples of blood from various different parts of that crime scene. >> they first had to determine if all the blood had come from darrell north. >> when the assailant is wielding a knife, and he stabs a victim, oftentimes, that knife

blade hits bone and it stops. and oftentimes the killer's hand continues its movement and slides down the blade and can cut the assailant. >> the other clue they looked for was shoe prints. with so much blood, both the killer and the victim would have stepped in it. crime scene technician jim varnen found several shoe prints and tried to enhance them with a special dye. >> amino black works because it stains proteins. and it's applied to protein stain, in this case, a blood stain. >> in several of the enhanced prints, analysts could clearly see the word "justin," a well-known brand of texas-made boots. >> we knew these footwear impressions in blood that had the pattern of a justin heel was most likely going to be from our assailant because it did not match the only other bleeder at that crime scene, which was our victim.

>> unfortunately, these boots weren't unique. >> how common are they? you're probably not from here if you don't have a pair. >> and it was impossible to tell the size of the boot from the print. >> in a justin boot heel, it is possible that you're going to have one physical size that would overlap into several different boot sizes. >> nevertheless, investigators asked both suspects, bob johnson and pool contractor curtis pope, if they owned a pair of justin brand boots. bob johnson owned a pair. but the heel of his boots was larger than those at the scene. curtis pope also owned a pair of justin brand boots, which appeared to be new, and willingly turned them over to investigators. >> in this case, my result was inconclusive. i could not eliminate or identify the boot as having made that mark. >> when investigators talked with pope about his boots, they

noticed something they hadn't seen before. some bruising under his eye. >> there was no cut, but it was a slight bruising. >> a background check revealed pope's business was faltering. >> he had a reputation of just not being very good at what he did, as far as the construction of the swimming pools. >> pope's business records indicated he was deeply in debt, wasn't able to pay his suppliers, and the only big client he had left was darrell north. if darrell fired pope during their meeting, it would have been the end of pope's company. >> pope's finances were in terrible shape. he was on the fine edge of disaster all the time. >> with a warrant, investigators searched pope's home computer and found something suspicious. >> someone on that computer had visited a website on how to beat

a polygraph and had, in fact, paid money to download a book on how to beat it. >> as testing continued on the blood stains on the floor of the crime scene, investigators noticed one blood drop on darrell north's pants that they had previously overlooked. >> there was a vertical drop on the back left pant leg of darrell north, while he's laying on the floor. >> the shape of the drop was perfectly round, meaning that the origin of the blood was stationary, and hit the fabric at a 90-degree angle. >> the significance of such a drop falling and hitting the pants perpendicularly while mr. north is on the floor is that it would mean that the assailant is standing above him, bleeding on him, after he has been attacked. so it puts a sequencing to the events. >> max courtney cut out the stain and submitted it for dna testing.

investigators found five other drops of blood at the scene perfectly round in between darrell's body and the door. >> i said, why not let's just test these five particular drops of blood that we know or we feel like didn't come from darrell north. >> tests confirmed the blood was not darrell north's. there was only one question that remained. who left the blood? one of the two suspects or someone else? beta-glucan... of a soluable fiber from whole grain oat foods like cheerios can help lower cholesterol. thank you!

this tiny drop of blood on the back of darrell north's pants told an important story. since the blood hit darrell's pants at a 90-degree angle, it meant the killer was standing over darrell's body while he was bleeding from his own wound, and he continued to bleed as he left the scene. >> when we observed those vertical drops of blood leading away from mr. north's body, that was a very significant thing for us to find because we knew then that the killer's dna was going to be present on that scene. >> and there was a possible explanation for how the killer was injured. the dented two-hole paper punch unit found near darrell north's body.

darrell may have used it to defend himself, causing an injury, a facial cut, or nosebleed. to identify the killer, dna samples were collected from the two suspects, bob johnson and curtis pope. dna testing revealed it was curtis pope's blood at the crime scene. >> if darrell north had not taken some steps to defend himself, this case wouldn't have been solved. >> would have never dreamed that, you know, firing somebody, you know, would cause somebody to, you know, go postal. >> darrell's family couldn't believe that the man whom darrell had mentored in business and treated in many ways like a son could have done this. >> not until the day they came out here to the house and told me that it was his dna that had been identified did i really believe. >> the bruises police noticed under pope's eye were probably the result of the fight.

>> and i was able to examine his arms and his hands for injuries. he didn't have any. there was no cuts. >> on the night of darrell north's murder, the dallas/ft. worth area was hit with a driving rainstorm, causing flash floods and power outages. the storm was so bad, darrell sent his construction crew home early, but he stayed behind because he had a 5:00 p.m. appointment with curtis pope. they were going to discuss quality problems with the swimming pool pope was installing at the hotel. pope was having financial problems. his company was headed towards bankruptcy, and darrell north was his only large client, although it's unclear whether darrell knew this. no one knows what the two men said to each other. but prosecutors believe curtis

pope snapped and attacked darrell with a knife. darrell was caught off guard, and struck pope in the face with a paper punch, causing the nosebleed. pope stabbed darrell over 40 times. as he lay dying on the floor, a drop of blood from pope's nose fell on to darrell's pants. >> there's no way he could have explained away how his blood was dripped on to darrell north's pants. >> we knew we had eliminated any possible innocent explanation for his blood being at the scene, and we felt like we had him. >> curtis pope was arrested and charged with first-degree murder. he posted bail, but on the first day of his trial, pope didn't show up. >> we learned through an informant that he was headed toward canada.

>> that afternoon, police in watertown, new york, just 25 miles from the canadian border, stopped a car from driving the wrong way down a one-way street. it was curtis pope. he tried to run but was arrested at a shopping center. curtis pope was returned to texas. he stood trial and was convicted of first-degree murder. he was sentenced to life in prison. it was an unusually bloody crime scene, but darrell north unwittingly provided the evidence needed to convict his killer. >> he probably bloodied curtis pope's nose. we have always thought darrell helped to convict curtis pope. >> the forensic evidence in this case was absolutely the linchpin of the entire case. >> this case stands out to me because it is one of the best of the uses of dna, combined with

blood stain pattern analysis, where working together, the two show who the blood came from and provide a scenario about which it possibly got there. breaking news this morning. arthur becomes a hurricane gaining strength as it spins up the east coast. communities evacuated. dangerous waves from the storm rolling in now. indra petersons is live with the track and what it means for your holiday weekend. >> terror in the skies. homeland security adding extra airports. terrorists may be developing explosives. protesters pushing away buses full of undocumented