thomas sprayed the notes with ninhydrin, a chemical that acts with the amino acid in perspiration, weers into an envelope and under the conditions, the prints will develop like a photograph on photograph paper. >> it revealed that dorothy was not sweating when she wrote the notes. something that usually occurs when someone intends to end their own life. >> and told him, that they needed to take another look at this case. because there was something wrong. >> but perhaps, the largest proof came the envelope flaps. who had licked them? >>> investigators wanted to know who had licked and closed the envelopes that held dorothy davis' suicide notes. to find out scientists needed dorothy's dna for comparison. unfortunately her body had already been cremated so they had to reinstruct her dna profile. >> her dna type was determined by cross referencing the possible types that she could have received from the mother and father and looking at the resulting types that she donated to both of her children. >> chris' dna profile was on file as part of his military records. scientists cut a small pi

. >> after having applied ninhydrin to the seat belt and allowing it to dry completely, i reexaminedhe seat belt for the presence of fingerprints and found none. >> but the killer left behind one piece of evidence. a 9 millimeter bullet found on the floor of the victim's jeep. when investigators searched henry sullivan's apartment, they found a 9 millimeter pistol. >> investigators found that sullivan was in possession of two 9 millimeter pistols, and that matched with the murder weapon that investigators had been looking for. >> one was inoperable. the other 9 millimeter handgun was test-fired into a tank of water. that bullet was microscopically compared to the 9 millimeter slug found in the van dusens' jeep. analyst erica henderson carefully examined the distinctive marks called lands and grooves made when each bullet goes through the barrel of the gun. >> when you look down the barrel of a firearm, you will see the ridges and valleys. these ridges and valleys, once a bullet is fired, will be imported on the bullet. so the bullet will also have these ridges and valleys. >> the tes

. >> investigators tested the letters with ninhydrin, a chemical solution which reacts to the amino acidsints. after it was applied, the documents were dried thoroughly. scientists found numerous fingerprints on the two documents, but none matched brad brisbin. they weren't larry moore's fingerprints, either. next the letters were analyzed by a forensic document examiner. both letters were typed with the same typewriter. the paper was inexpensive, the kind often used in high schools. the type showed no defects, making it difficult to identify the typewriter used to create them. and only the signature was handwritten. >> the signature itself is a full cursive signature. it is full of tremor. it looks labored and it looks slow, and it does not look like it is the product of habitual movement. >> experts compared this questioned signature to several documents brad signed shortly before his disappearance. >> the upper case b in the name brad was actually constructed in three pieces. there is a break. it has the up and down spine on the left side of the letter, but between the top and the bott