man: bethany ann doke... [applause] ian donnelly... [applause] kirsty lynn dutehead... >>> for 13 years, the murder of biotech 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 rae action 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 destr

man: bethany ann doke... [applause] ian donnelly... [applause] kirsty lynn dutehead... >>> for the first time in the history of forensic science, a cast made of the inside of a gun was used to identify a murder weapon. the pistol used to kill cliff merck had been sold to a drug dealer by robert and gerald cowan, but for some reason, the cowans' fingerprints did not match those found at the crime scene. >> the person who attempted the comparison was then able to make a match, and he failed to have another examiner verify his conclusions. >> this was a breach of protocol. the standard operating procedure in all crime labs requires a fingerprint examiner to have someone verify his or her conclusions. so the fingerprints were resubmitted for analysis, and this time, the results were verified by a supervisor. the fingerprints found in the mecks' home matched robert cowan. >> it goes without saying that i was highly irritated and embarrassed for the department. >> i initially on the latent evidence being misread, i tend to believe that was p