This case study gives students an opportunity to draw a conclusion about an actual crime that was prosecuted in Louisiana. A physician was accused of intentionally infecting his ex-girlfriend with HIV-tainted blood drawn from a patient in his practice.  The scientific investigation uses bioinformatics tools and relies on the ability to interpret phylogenetic trees.  Students develop hypotheses about the crime, then use sequences and online tools to generate a phylogenetic tree to test the hypotheses and render a verdict.  The authors have designed and implemented three parallel cases - one for Grades 5-8, one for Grades 9-12, and one for upper-division undergraduates, specifically for a course in molecular evolution.  This is the Grades 9-12 version.