Smyth was born in Northern California and started his career in the female-fronted five-piece melodic death metal band Ariah in 1988.

[3] In the next five years, Smyth toured with Testament all around the globe and played uncountable shows as a member of the band, although he never recorded and album with them.

[4] On the other hand, Smyth formed the band Dragonlord as a side project with guitarist Eric Peterson and bassist Steve DiGiorgio of Testament in 2000.

On April 30, 2006, Smyth released a message explaining to fans that he has been diagnosed with kidney failure due to a congenital birth defect.

[7] Steve started an international metal band with classic and modern influences, featuring members carefully selected by Smyth: Mikkel Sandager (Mercenary) on vocals, Jamie Hunt (Biomechanical) sharing guitar duties, rounded out by a powerhouse rhythm section with Tomas "O'Beast" Koefoed (MNEMIC) on bass guitar and Michele Sanna on drums (although former drummer Raphael Saini of Italian band Chaoswave played on the album).

[9] In 2014, Smyth joined the thrash/death metal supergroup From Hell alongside Damien Sisson of Death Angel and Paul Bostaph of Slayer.