At about 5.30pm on Tuesday 22 September 2015, a man boarded a route 886 bus on Marangaroo Drive near Farnell Place, Alexander Heights.
During the journey, the man used a green marker pen to draw a graffiti tag on the rear of a bus seat.
The man got off the bus near a shopping centre in Ballajura.
Police have released a CCTV image of a man who they believe can assist them with their inquiries.
The man is described as:
- Light skinned
- 170-180cm tall
- 20-25 years old
- Medium build
Wearing a grey jumper and black pants.
If you know the identity of this person or have any information about this offence make a report online or call Crime Stoppers on 1800 333 000, where all calls are strictly confidential, and rewards are offered.