FBI Using SNP DNA Testing in Nancy Guthrie Case? This Could Change Everything The FBI may be using advanced SNP DNA testing in the Nancy Guthrie case—and this could change everything. When traditional DNA fails, this “snip” technique can identify suspects in ways never before possible. Retired NYPD Sgt. Bill Cannon breaks down how SNP DNA works, why CODIS may not have produced a hit, and what this means for investigators working inside Nancy Guthrie’s home. Could degraded DNA still hold the key? Is the suspect already hiding in plain sight through genetic connections?