>> i feel that kiesha solved the case, along with the detectives. and she provided the evidence against andrew rich. she got her man. just weeks before testifying at a criminal trial, one of the key witnesses, a brilliant research scientist, was murdered. for 15 years, there were many suspicions, but little proof. ironically, advances in the very research the victim had been working on helped nail her killer. when you ask friends and colleagues about helena greenwood, you hear words like brilliant, quiet, honest and a hard worker.

helena earned a ph.d. in microbiology and was an executive in the biotech industry. >> she was not only an excellent scientist but she had marketing skills. and those two things often are not concurrent. >> helena was very forward thinking, especially looking at technology. but she also knew the power that technology by itself doesn't market a product. basically it's the human need. if there's a human need, there's a product. that's required. >> helena and her husband, roger, a landscape designer, lived in atherton, a quiet suburb outside san francisco. our story begins on a saturday night in april of 1984 when roger was out of town on a business trip.

in the middle of the night, a man suddenly appeared in helena's bedroom and threatened to kill her. helena was sexually assaulted, then robbed before the assailant made his getaway. >> dr. greenwood described her assailant as being fairly tall, slender, athletic, with a complexion, perhaps, of part half black or a hispanic person, an olive complexion. she couldn't see his face because he had a hooded sweatshirt pulled up so that only his eyes showed. >> the assailant entered the home through a kitchen window. but it was helena's friend who found a key piece of evidence that police had overlooked. outside on the deck near the kitchen window was a teapot from helena's kitchen. fortunately, the friend had the good sense not to touch it.

>> that teapot was taken into evidence, taken to the crime lab and fingerprints were developed. imagine the teapot, there were three fingerprints in this position as though someone had picked up the teapot from the windowsill and placed it on the deck. >> helena told police she made tea before going to bed, then placed the teapot on the windowsill. it appeared the assailant moved it before crawling through the window. unfortunately, the fingerprints didn't match any on file with the police department. with no other leads, the case went unsolved until one year later. >> a man was arrested while exposing himself to a 12-year-old girl outside an apartment in belmont, california. that suspect was david paul

frediani. >> belmont was only seven miles from helena's home. the suspect, david paul frediani was a 42-year-old accountant with no prior arrests. since frediani resembled the man helena described, police compared his fingerprints to those found on helena's teapot. they matched. >> one of the things i asked him was -- he had denied even being involved in the initial sexual assault against mrs. greenwood. i remember asking him, you never assaulted this woman? he said no, i never did any of that. >> they then told him we have your fingerprints. at that point, according to the detective, he took a deep breath, let it out, began trembling. he could actually see his chest moving in and out and made a statement as to the effect of i was really drunk when i did those things. he then asked for a lawyer and refused to make any more statements.

>> at the preliminary hearing where both helena and frediani were present she was asked if she could identify him and she couldn't. not positively. and out of that arises one of the great mysteries of this whole case. >> but the fingerprints on the teapot were all the prosecution needed, so the case headed to trial. sadly, helena greenwood didn't live long enough to testify in court.

while her sexual assault case was pending, helena greenwood and her husband, roger, moved from san francisco to san diego. she took a new job with gen-probe, a biomedical research firm that was looking for ways to diagnose disease through dna. one morning before work, helena was at home on the phone, making last-minute preparations for an important company meeting. but on this day, she never arrived. co-workers called helena's husband at work. he immediately drove home and

found the front gate locked. when he peered over the fence, he saw his wife's body. >> roger was in total shock. and he first called gen-probe. he didn't call the police. he called gen-probe. that shows how disoriented he was. >> the crime scene appeared to be staged. it had the earmarks of a robbery, but no money was missing from helena's wallet. >> you had her purse that was strewn about. they preserved all of that for fingerprints or other evidence, of which, unfortunately, there were none. >> there was no physical evidence left. obviously, he wore gloves. i mean, one safely can assume that, i guess. >> and it was clear that helena valiantly fought her attacker. >> this woman put up a hellacious fight. it was evidenced by the fact that her fingernails, two of them were found at the scene. she had broken off two of her fingernails while scratching

this person. >> at the autopsy the medical examiner discovered petechial hemorrhages in helena's eyes, an indication of strangulation. there were no signs of sexual assault. but under helena's fingernails were tiny traces of what appeared to be blood. unfortunately, the sample was too small for forensic analysis. >> what comes to mind when there's a bizarre murder, strangulation in broad daylight? you think marital trouble. you think crime. you think drugs. i mean, helena never got within a thousand miles of any of those things. and that simply deepened the mystery. >> helena's husband, roger, was the first person police interviewed. >> whenever a woman is killed the prime suspect is generally the husband. and statistically, that bears out. most women who are killed are killed by someone well known to

them, usually a romantic interest. and the husband is often the perpetrator. >> roger said he left home at 8:00 a.m. and was at work at the time of his wife's murder, around 9:00 a.m. records indicated helena had been on the telephone until 9:00 a.m., about the time a neighbor heard a commotion. >> one man who lived next door said about 9:00, when he was shaving, he thought he heard a human -- an abrupt human cry. but who knows. >> when police confirmed roger was at work, 40 minutes away at that time, he was eliminated as a suspect. helena's murder also meant that she would never testify at the sexual assault trial back in san francisco. >> got a call from roger franklin who was good greenwood's husband.

roger told me that his wife had been murdered in san diego, the san diego area where they had moved after the sexual assault. that was a sickening moment, because he also told me that her purse was found near her body, her car keys were there, her credit cards were there. didn't appear that there had been a robbery. >> david paul frediani, the man accused of helena's sexual assault, had been out on bail at the time of helena's murder, but insisted he was 500 miles away in san francisco. investigators were naturally suspicious. >> he was the only person who conceivably had a motive for doing this. >> the prosecutor refused to drop the sexual assault charges against him. but everyone wondered whether the prosecutor would ever get a conviction now that his witness was dead.

conviction now that his witness ♪

what is this place? where are we? this is where we bring together the fastest internet and the best in entertainment. we call it the x1 entertainment operating system. it looks like the future! we must have encountered a temporal vortex. further analytics are necessary. beam us up. ♪ that's my phone. hey. [ female announcer ] the x1 entertainment operating system, only from xfinity. tv and internet together like never before. just three weeks before she was scheduled to testify in her sexual assault trial, helena greenwood was murdered in her front yard. david paul frediani went on trial as scheduled for helena's sexual assault. prosecutors had his fingerprints

on helena's teapot. and they also found serological evidence. >> we also presented evidence that the semen on the pillowcase in helena greenwood's bedroom, first, that it was semen and, second, it was from a type o, individual, who was a secreter, and a pgm type, a mutase of one-plus all matched frediani's abo type. >> dna testing was still in its infancy. at the last minute when faced with the fingerprint and serological evidence, he pled no contest to the assault and was sentenced to five years in prison. but frediani said he was innocent of her murder. >> they knew who killed helena

greenwood and they knew it was david paul frediani, but they couldn't prove it. >> eventually helena greenwood's murder was relegated to san diego's cold case files and forgotten. over the next several years, helena's parents died, her husband, roger, developed cancer and he, too, passed away. >> and who is there to mourn for helena? very few and growing fewer. >> and gen-probe went about the work helena had been pursuing before her death, looking for ways to use new dna technology for quicker, faster medical diagnoses. david frediani served only three years of his five-year sentence and was released. he returned to his accounting practice. >> this is a very egotistical, self-centered, obviously

sociopathic person. hey, i just got away with murder, you know. his life went on and he prospered. >> and that's where the case stood for another ten years. until investigators in san diego's cold case unit decided to take a second look at helena greenwood's murder. and deep in helena's file was a piece of information that immediately caught investigators' attention. seven days before helena's murder, david paul frediani was involved in a minor traffic accident in southern california not far from helena's home. >> the defendant had no business being in southern california. we knew he knew she lived down here. although we didn't know how he had that information. but it just seemed a little bit strange that he's awaiting trial, he lives in san francisco and he takes a trip down to southern california.

>> as detectives look through the evidence, they noted there was a tiny speck of blood under helena's fingernail. at the time, far too small for dna testing. had forensic science advanced to the point that it could identify a speck of blood almost too small to see? ♪

what is this place? where are we? this is where we bring together the fastest internet and the best in entertainment. we call it the x1 entertainment operating system. it looks like the future! we must have encountered a temporal vortex. further analytics are necessary. beam us up. ♪ that's my phone. hey. [ female announcer ] the x1 entertainment operating system, only from xfinity. tv and internet together like never before.

for 13 years, the murder of bio-tech research scientist helena greenwood went unsolved. the medical examiner found what looked to be blood under one of her fingernails. at the time, it was far too small for dna analysis. by 1998, however, work that gen-probe and scientists like helena greenwood had been working on led to new developments in dna testing. one of the most important was polymerase chain reaction or pcr which enabled scientists to copy minute dna samples until they were large enough to test. >> polymerase chain reaction allows you to make dramatically

increasing number of copies. you start with one after one round of pcr, you end up with two, then four, then eight and so on. the big advantage of pcr for forensic work is that it is so sensitive. very small amount of dna can yield a very large amount of information. >> it's a fortunate thing that they didn't try to test it at the time, because as you test biological material it's destroyed. had they, at the time of helena's autopsy, tested that material, they would have found nothing and the material would have been destroyed. >> when the biological material from helena's fingernails was tested using pcr, scientists made an important finding. >> on some of the fingernail clippings, they found only dna that was consistent with dr. greenwood's. and on one of the clippings, they found dna that was essentially pure, not from dr. greenwood at all. that's when they got very interested.

of course, the possibility is that that's the perpetrator's dna. >> and investigators found even more evidence on helena's clothing. on her nylon stockings were grab marks. they decided to test that area for microscopic traces of blood and found some. the dna from helena's fingernail and stockings was compared to a blood sample from david frediani. and here are the numbers. the odds that the dna under helena's fingernail and stockings was someone other than david frediani's was one in 23 billion. he could hardly believe it when police arrested him. >> mr. frediani came out of his house and began walking to his car. that's when we approached him and placed him under arrest. his reaction was all the color just rushed from his face. he turned white.

i think he knew at that point that he wasn't going to be looking over his shoulder anymore, it was over. and great satisfaction for us. >> david paul frediani was charged with first-degree murder. >> one of the tragedies, many tragedies in this case is that roger never lived to hear that frediani, who he knew had done the murder, he never lived to hear that san diego authorities were able to identify mr. frediani as the murderer. >> prosecutors believe frediani murdered helena in the mistaken belief that her death would end the sexual assault case against him. >> he wasn't smart enough to understand that just because he killed mrs. greenwood that her preliminary testimony was still going to be used. he didn't realize that. that was the error in his plan. >> he drove 500 miles from his home in san francisco to

helena's home in san diego to stalk the couple and learn their schedules. his first mistake was getting in a car accident a few days before the murder, proof that he was in san diego before the crime. frediani learned that roger left for work every morning around 8:00 a.m., about an hour before helena. prosecutors believe frediani waited for helena outside her front gate. he was wearing gloves to avoid leaving fingerprints, like he did when he assaulted helena a year earlier. when he heard helena close the front door, he made his move. frediani probably believed the gloves would protect him and didn't realize he left crucial forensic evidence behind. ironically, it was helena who grabbed it.

>> i can only imagine what was going through helena's mind, that this man who assaulted her is obviously coming to do harm to her. maybe it's just a little too much to think but she scratched the heck out of this guy. we know she did. i almost wonder like, hey, i'm going to leave some evidence behind to show who my killer was. i survived this but by god i'm going to leave something behind to tell you who killed me. i think that's what happened in this case. >> at the trial under cross examination, frediani admitted to the sexual assault but he did not confess to her murder. regardless, he was convicted and sentenced to life in prison. >> we expect victims to testify. and that's what helena greenwood did. she testified against the defendant at the preliminary examination. then he tracked her down and he killed her.

and no conviction is justice for what happened to her. but ironically, the science that she was working on, in fact, helped to put away her killer. breaking news overnight. massive protests turn deadly in two countries. people in ukraine and venezuela, rising up against their governments. flaming shooting in the air, tear gas sending crowds scrambling. we're live with the cast of confusion that all unfolds this morning. good morning, welcome to "early start." i'm christine romans. >> and i'm john berman. it's 5:00 a.m. in the east. a lot going on this morning. we begin in the ukraine. these are live pictures from the ground. this morning, kiev's main square son fire. you can see the smoke there. you can see the water cannons in the