A Drop of Blood, a Plastic Fork, and Fourteen Years

Irasema Chavez was stabbed more than 100 times in her Arlington, Texas, apartment in January 2012. After CODIS produced no hit, FBI investigative genetic genealogy pointed to her friend Mayra Velasquez; police later matched crime-scene blood to DNA from a discarded fork. Velasquez was charged with capital murder, has pleaded not guilty in public, and the case now turns on what a single stain can—and cannot—prove.