Prior to becoming a barrister, Mr. Walker was a private criminal defence solicitor. He was also previously a Federal Prosecutor who represented the Commonwealth Director of Public Prosecutions in large scale drug importation and sexual offences. He appeared in the matter of Croation soccer star Marko Simic alleged to have committed an act of indecency on an international flight Football star Marko Simic accused of assaulting a woman on flight to Australia. He also appeared in a matter concerning the importation of approximately 300kg of ephedrine imported into Australia Police find 300kg of ephedrine inside highlighters from China.
Mr. Walker was a former Australian Federal Police Member who represented and appeared for the Commissioner of the Australian Federal Police in NSW Supreme Court proceedings. This included forfeiting approximately $220,000 in proceeds of crime in The Commissioner of the Australian Federal Police  NSWSC 1737, and approximately $400,000 in another matter Application by the Commissioner of the Australian Federal Police  NSWSC 1302. Mr. Walker has also written an article concerning proceeds of crime for Lawyer Monthly.
Mr. Walker previously worked as an Investigator at the Australian Taxation Office in the Private Groups & High Wealth Individuals – Offshore Tax Evasion department and has been part of the Criminal Assets Confiscation Taskforce which was a joint taskforce between the Australian Federal Police, Australian Taxation Office, Australian Criminal Intelligence Commission, Australian Transaction Reports and Analysis Centre and the Australian Border Force. The purpose of the Criminal Assets Confiscation Taskforce is to enhance the identification and pursuit of potential criminal asset confiscation matters.