investigation. the letters roc smeared on a wall matched karen s former boyfriend roc. and soon a forensic break through would force detectives to reconsider the bloody clue. not only what it meant but who wrote it. here again is dennis murphy. reporter: the handwriting was on the wall and forensic specialist ana cox was intent on breaking down the key piece of evidence implicating karen s first boyfriend roc. you would spend hours looking at these letters. you actually cut the sheetrock out of the place and took it into your lab? yes. i have to look at those letters, at everything about them. using a high powered microscope ana did an analysis of the specks of blood as karen was stabbed 16 times. that flow spatter served as a