Complaints often arise from incidents in police interview rooms, police cells, during police raids and as a result of arrests. In many of these situations, there are no witnesses or no independent or reliable witnesses. Sometimes people who are the victim of, or witnesses to, such incidents are intoxicated by alcohol or drugs, are seriously traumatised by what happens, have themselves recently committed a criminal offence, are physically or mentally unwell or are intellectually disabled. All of these factors can make proof of allegations of police misconduct more difficult.

Often the police will admit the allegations, but will claim that their actions were justified; for example, that it was necessary to use force against the complainant because the complainant assaulted them or was resisting arrest. Police generally work in pairs, and often in larger groups. It is therefore typical for more than one police member to provide a sworn statement, or to give evidence in court, in relation to the incident. However, what they say may be contrary to the version of facts put forward by the person complaining.

It is rare for police to give evidence against other police in the context of a complaint by a citizen. Thus, a member of the police may swear statements that are inconsistent with those of a citizen who is not in a position to produce independent corroboration, and who may have been charged with a related criminal offence.

The police will probably have written records relating to what happened between you and them, especially if the incident about which you are complaining resulted in your receiving criminal charges. In addition, it is worth bearing in mind that police are repeat players, that is, they are accustomed to giving evidence and responding to questions. You probably are not.

As noted above, prompt lodging of a complaint improves the chances of investigative success by the ESD or the OPI. However, there may be disadvantages in complaining if the police have charged you with offences.

When a complaint is made, it is not unknown for charges, or additional charges, to be laid by the police involved. In addition, the tendency is for there to be less room for negotiation directed toward having the police withdraw charges or proceed with lesser charges.

It is also a common experience for prosecutions to be more aggressively pursued when a complaint has been made against an informant, a corroborator or another police member involved in the police investigation.

If the police have charged, or are likely to charge, you with an offence related to the incident you are complaining about, you should always get legal advice before providing details of your complaint to police, including the ESD.

In addition, while it is itself a disciplinary offence for a member of the ESD to release statements of complaint to prosecuting police, there are many who would say that this happens with some regularity.

All of these reasons can make it advantageous strategically for a person who has been charged with criminal offences either not to make a complaint against police or to delay lodging it until after criminal proceedings brought by police have concluded.

Generally, if you have spent time at a police station, either in custody or voluntarily, you are entitled to make a complaint there and then. If you indicate your wish to make a complaint, the officer-in-charge, usually a senior sergeant, is required to take the complaint or to refer it directly to a duty inspector. The complaint can be made at any time of the day or night, at any stage in the interview process or at any other time while you are at the police station or are in police custody.

Before releasing anyone questioned or charged from the police station, the officer in charge is required to enter that person's name into an Attendance Register. The person is customarily asked whether they have any complaint about the quality of treatment while in police custody. Anyone who does have a grievance about their treatment should be asked to provide further details or to await the arrival at the station of the duty inspector. This can take some time.

Many people who have a complaint to make say that they have no complaint because they are keen to leave the station or because they are scared of making the complaint to the immediate superior of the person they are complaining about or to the very person about whom they have a grievance. However, it should be understood that failure to complain at the station is routinely used by police to attack the credibility of the complainant when they later make their complaint.

An option is to state clearly at the time that the Attendance Register is being filled that you do have a complaint to make, but that you intend to make your complaint after being released and taking legal advice. If you are not sure that you will lodge a complaint, ask the person filling in the Attendance Register to write under your name, "Yes, but I wish to seek legal advice before making a formal complaint". In this way, you are not committed to any course of action, but the way is open for you to complain if you wish to and you have indicated your early intention to complain.

Another option, but a less comfortable one, is for you to refrain from answering the question. Legally, you are under no obligation to answer the question or to sign the Register. The police are not entitled to detain you for failure to answer the question or to sign.