Jockey Josh Cartwright has been suspended for 18 months for his reckless ride aboard Senior Council at Morphettville on January 14.
Cartwright - who is dual-licensed - has also had his trainer's licence suspended for six months.
Thoroughbred Racing SA stewards handed down their verdict on Monday. Significantly, Thoroughbred Racing South Australia chief steward Johan Petzer emphasised that there was no evidence that Cartwright had placed a wager on Murti, the winner of the race ridden by Cartwright's girlfriend Anna Jordjso.
Petzer also ruled out any suggestion of an argument in the jockeys' room earlier on the day of the incident, which had also been rumoured as a possible trigger. Petzer did however state that he had never seen "such severe interference" on a racecourse.
Cartwright pleaded guilty to a charge of reckless riding under AR 137(a) following a post-race inquiry into the incident where the rider intentionally made contact with other runners.
Under the particulars of the charge stewards said Cartwright 'directed and rode his mount outwards in a reckless manner at an acute angle with the intention of making contact with runners to his outside'.
Cartwright's mount Senior Council made heavy contact with Go The Journey ridden by Matthew Poon which in turn cannoned into House Of Wax to its outside.
The interference to House Of Wax resulted in jockey Jason Holder becoming unseated for three strides.
The bizarre incident, which attracted widespread media coverage, occurred in the final race of the day on January 14.
Given the seriousness of the charge stewards stood Cartwright down from all riding duties while the inquiry was adjourned to consider the penalty.
The 22-year-old has ridden nine winners for the season at a strike rate of 12 per cent.