During the Borg Invasion of 2381, Cmdr. Briggs was attending a medical conference on Coridan III, and as an able-bodied medical professional, he was quickly pressed into providing medical aid to the wounded. When he came across a Borg drone undergoing the Caeliar transformation process, he killed it, inadvertently kicking off the catomic plague that spread across three worlds.
Cmdr. Briggs spent the next year of his life trying to cure the plague, while simultaneously attempting to weaponize catoms for if the Caeliar were ever to return as a threat to the Federation.
On April 5, 2382 (First Contact Day), Cmdr. Briggs' actions were exposed by Seven of Nine, along with Lieutenant Commander Tom Paris, Dr. Sharak, Lieutenant Samantha Wildman with assistance from the Tamarian Embassy and the Cardassian Ambassador to the United Federation of Planets Elim Garak, and he was arrested under orders from the Commander-in-Chief of the Federation Starfleet Fleet Admiral Leonard Akaar.
With Cmdr. Briggs' arrest, numerous subordinates were questioned about their level of knowledge and complicity in his illegal activities, while both the heads of Starfleet Medical and the Federation Institute of Health were asked to resign by President of the United Federation of Planets Nanietta Bacco. (VOY novels: Protectors, Acts of Contrition)