Kristin Song, whose 15-year-old son Ethan was killed in 2018 after he and a friend handled an unlocked pistol, will testify. Other witnesses include Maya Haasz of the Children’s Hospital Colorado Anschutz Medical Campus, Ted Bonar of End Family Fire, Joseph Bartozzi of the National Shooting Sports Foundation and Stephen Willeford, a former National Rifle Association instructor who exchanged fire with the suspect in a 2017 mass shooting in Texas.