uh, NONE.
"The decision was announced Wednesday, nearly seven weeks after Stewart's car struck and killed Kevin Ward Jr. at a dirt-track race on Aug. 9 in Canandaigua. District Attorney Michael Tantillo also said Ward was under the influence of marijuana that night 'enough to impair judgment.'"
http://www.dailyamerican.com/prosecutor-driver-kevin-ward-under-influence-of-marijuana-night-he/article_c164ab5a-441d-11e4-9151-0017a43b2370.html
Makes this story both sad and crazy.