but in the case of the linden lake skull, scientists got a genetic break. they discovered that the killer removed all but two of the wisdom teeth, which had been embedded in the gum, which the killer may not have seen. >> when the perpetrator pulled the teeth, he didn't realize those molars were up underneath the gum line. so those were protects and preserved. >> dr. murray extracted tooth pulp from the wisdom teeth and sent it for dna testing along with a blood sample from tina's 18-month-old son. but scientists could not obtain a usable dna profile from the tooth pulp. >> it's possible that the reason is that the teeth were still unformed. and when teeth are still forming, their roots are open, open cavities. >> it was also possible that tiny single cell microorganisms in the lake called diatomes damaged or altered the cells in the tooth pulp. as a last resort, dr. murray tried to extract dna from the skull itself with a surgical drill. she carefully removed six bone samples from the thickest part of the skull. >> with sterile techniques, the middle secti