Wow, after reading this thread, without having a go at anyone who has offered an opinion on what constitutes a criminal record, all I can say to anyone reading this thread is there is a considerable amount of opinion posted that is just plain wrong.
I'll preface my comments by saying thatI am not an immigration officer or DFAT official. I did spend 30 years in the NSW Police and retired as a Detective Superintendent a few years ago, so I do have a little bit of experience in the criminal law and what constitutes a criminal record etc. and a basis for my comments.
Advice that a conviction is spent after ten years and doesn't have to be disclosed is incorrect. The only convictions that are ever expunged from a criminal history are those ordered by a court. This is the same in all states and territories. Unless a court has ordered the record be removed and the fingerprint record for that arrest destroyed, that matter will remain on your record for life. They don't disappear from your record. Ever.
The police have two types of criminal histories they can produce. The first is known as a bail report in NSW, (it may be called something different in other jurisdictions) this report shows EVERYTHING. Every arrest, conviction, acquittal, warrant, summons, fine, gaol sentence, bond, failure to appear, non conviction etc. The purpose of this report is to allow a court or authorised bail officer to view everything that is relevant to the question of bail. The second type of criminal history will only show convictions, and fines and is used by courts to consider for the purpose of sentencing. Traffic convictions and fines are generated on a separate report.
One thing to note about criminal records. Strictly speaking, for a matter to form part of your criminal record, it must be linked to your fingerprint record. If an arrest or conviction is not matched to a fingerprint record, then it cannot be proved. From time to time, erroneous entries can appear on a person's criminal history if someone has used the same name and date of birth. This happens more frequently than you might think, particularly among family members or some ethnic backgrounds. I have seen courts have no option but to disregard a criminal conviction because the conviction was not linked to a fingerprint record. This can occur where a person was initially summonsed or given a court attendance notice rather than arrested and charged (where fingerprints are taken as part of the charging process). If you obtain a criminal history check prior to applying for a visa and you found a matter on that record that was not linked to fingerprints, you could seek to have it removed on the basis that the conviction did not relate to you. (If that was the case). There is no way an entry can be proved as belonging to you without the matching fingerprint record.
Don't be mislead into thinking that the US Government can't access your criminal history. Australia has various treaties and intelligence sharing agreements in place with the US and other countries. While this doesn't mean that the US Government has direct access to the criminal indices of a state police force, it does mean that they can get a copy of your record by requesting it from the Australian Government. We have a number of Australian Federal Police liaison officers spread around various overseas embassies and the AFP have an International Division in Canberra which handles information requests from other countries among other things. I have no doubt when applying for a visa waiver, the US would be asking Australia for a copy of your record either through DFAT or the AFP.
The question on the ESTA is not whether you have a conviction, its whether you have ever been arrested. Whether you choose to declare an arrest or not is up to you, but they can get the information if they need to. You might think the chances are pretty slim that you would be flagged, but you never know what might cause them to make a request to check your criminal history or trigger enhanced screening when you actually enter LOTFAP.
Just after I retired from the police, I took my wife and daughters to the states to do the Disneyland, sea world, Vegas family holiday. I had never been to the states before. Coming into LAX, I was separated from my family and subjected to enhanced screening and interviews for nearly two hours. Things were not looking too good, lots of checking on their NNI database, furtive conversations with supervisors etc. things got really interesting when an ICE team in full tactical gear came in to keep me company. Finally one of the immigration officers said "have you ever had any interaction with law enforcement." So I told them I was a retired police officer. Well, everything changed and suddenly it was all good, all smiles and apologies for the misunderstanding. Seems some bone headed Hells Angel bikie and I share the same name and date of birth apparently, even though from their questions this knucklehead has several tattoos and I have none. The point is, all it takes is a case of mistaken identity or some other reason you get flagged and subjected to more rigorous vetting. Once that happens there is the possibility that they might find out that you omitted to tell them some things you really should have and you could find yourself on the next plane out.