Cannington Detectives are investigating an incident that occurred around 1am on Sunday 5 July 2020.
The incident occurred near the intersection of Tighe and Kew Street in Cloverdale and resulted in a man who was riding a motorcycle (not stolen) being injured.
Detectives are seeking to establish the movements of all associated parties before and after the incident, and whether an item was thrown at the rider.
The 18-year-old rider was conveyed to Royal Perth Hospital where he is in a critical but stable condition.
Detectives are asking anyone with information or who has CCTV, dash-cam vision of the area around the time of the incident to come forward and contact Crime Stoppers on 1800 333 000 or report online at www.crimestopperswa.com.au. Members of the public reporting information to Crime Stoppers may remain anonymous if they wish.