“A case of mistaken identity” may drive the plot of the latest spy film or crime novel, but it’s only a tale of trouble for geneticists, oncologists, drug manufacturers and others working with mouse cell lines, one of the most commonly used laboratory model systems for genetic research. Cell lines that have been contaminated or misidentified due to poor laboratory technique and human error lead to inaccurate research studies, retracted publications and wasted resources. In fact, many scientific funding organizations, such as the National Institutes of Health, now require scientists to verify their cell lines for identity and quality before research grants are awarded.