Rachel Holden is a doctor and epidemiologist who published a series of articles concerning the fact that mankind had grown bigger in the last twelve thousand years with NCIS Tech Operator Eric Beale calling the nature of Holden's articles "disturbing".
In one such article, Holden claimed that by wiping out smallpox, the human race had made a decision that could lead to their undoing. She later decided to cut the world's population in half and save the planet by buying several vials containing smallpox from Dr. Jarrod Prodeman, her main goal being to use the vials in an attack of bio-terrorism to wipe out half of the world's population as she believed that the Earth had gotten overcrowded in recent years.
Despite her efforts which involved her giving out smallpox-infected t-shirts at a stand during the "International Leaders of Tomorrow" seminar, she was eventually arrested by NCIS Agents G. Callen and Sam Hanna and Hawaii Five-0 Detectives Danny Williams and Chin Ho Kelly.
After being arrested, it's presumed that she was jailed for planning to launch a possible biological terrorist attack against the U.S.