[Josy]

The bullet dna test was the one that was contaminated by Sherry's own DNA.

Agent Fassbender told crime lab analyst Sherry Culhane that she needed to “place Teresa Halbach in the house or garage.” She ran a DNA test on the bullet fragment and the control was contaminated which means the results are to be reported as “inconclusive.” Instead, she reported that Teresa Halbach’s DNA was found on the bullet. Of course, it is impossible to trust this evidence.