Danell formed Social Distortion in 1979 with frontman Mike Ness while attending high school together. Originally the group's bassist, Danell switched to guitar after some band defections, and helped define the group's signature jangle on such albums as Mommy's Little Monster (1983), Prison Bound (1988), Social Distortion (1990) and White Light, White Heat, White Trash (1996). He remained the guitarist for the band until his death, from an apparent brain aneurysm (Mike Ness stated on the DVD commentary of Another State of Mind that Dennis died from a heart condition), at his Costa Mesa, California home at the age of 38, while in the process of moving to his new home in Newport Beach.
"I am saddened beyond any possible form of expression," Ness said in a statement. "Dennis and I have been friends since boyhood, starting Social Distortion together while we were in high school. My deepest regrets to his family."
Danell also started a new side band called Strung Gurus, with Michael Knott of the Orange County band, Aunt Betty's (formerly on Elektra). Danell produced, co-wrote and played guitar for them, whilst working on their first full-length album. The Strung Gurus debut, to be the second release on Masterpiece Records, was nearly completed.
In an interview for the Strung Gurus promotional bio, Danell had said, "I am very excited about Strung Gurus because the music is high energy and commercial, but it does not sound like Social Distortion. The new band allows me to stretch as a songwriter and producer by tackling a sound outside my comfort zone." Rough mixes of four Strung Gurus songs were already in limited circulation and had started a buzz among fans and local journalists impressed with Danell's versatility and writing abilities.