The following is not legal advice but is for information only. Legal advice is when an attorney applies the law to a person's individual circumstances and advises them on their legal options or potential exposure to legal harm, which a web page clearly does not.
In a criminal case, a defendant is entitled to discovery, which allows them to obtain information and evidence held by the prosecution. This a broad subject that this web age cannot begin to explain fully. It has occupied legal scholars and taken up yardage of creaking shelf space in law books. However, this is a brief explainer that may help.
Discovery is an essential part of the legal system, ensuring fairness, transparency, and the ability to mount an effective defense. It allows the defendant and their legal counsel to gather the necessary information to challenge the charges and prepare a defense strategy.
Discovery is a process governed by two things - constitutional law and court rules. Even constitutional law is divided further because Maine and the United States have different constitutions - although in practice a lot of Maine’s constitution has been subcontracted to federal precedent. The distinction between case law - which deals with constitutional due process - and the enforcement of court rules is often muddied greatly and confused by prosecutors, judges, and even defense attorneys.
Court rules have no legal effect until a court acts. Judges have enormous discretion in how rules are enforced but the bottom line is that a court rule that is not enforced might as well not exist. Court enforcement for violations, when and if they are found, come in the form of a ‘sanction’ against The State of Maine - which means the police, some witnesses, or the prosecutor - who merely acts as a representative of the government (in the same way as a defense attorney acts on behalf of a defendant). This is how court rules are supposed to work in Maine. However, state actors (whoever they are) are often found to not disclose evidence that they should and when pointed out because it is discovered is often met with a shoulder shrug, no sanction is imposed, and there is little to no incentive to keep failing to disclose evidence. However, it is for all involved in the process to act properly - whether the reason is understaffing, overwork, mistake, inadvertence, or worse.
To add to the mix, case law in Maine at the state’s highest court also confuses these two things - constitutional case law and court rule. By way of example, the Law Court (Maine's highest court) says a defense attorney has to be diligent in doing their own work (called the due diligence rule) to find what’s at the fingertips of the government. This is in interpreting the enforcement of court rule - while also dealing with case law. But no United States Supreme Court case has EVER said there as obligation on a defense lawyer to act (quite the opposite - the Supreme Court had said discovery obligations cannot be delegated). Maine's case law is in need of correction. Until it is, defendants are stuck with these past errors.
Discovery can involve several different types of evidence, such as:
Witness Statements: The defendant is entitled to receive statements made by witnesses involved in the case. This includes statements made by both lay witnesses and expert witnesses.
Electronic evidence: Many (but not all) sheriff’s offices and police departments have video cameras that officers wear or have in their cruisers, and footage from them must be disclosed. They also routinely record 911 calls or phone calls with witnesses, dispatchers / radio traffic, or record on videos in police stations. This must be disclosed as well, particularly when requested.
Documentary Evidence: The defendant has the right to access and review relevant documents that are in the possession of the prosecution. This can include police reports, laboratory results, photographs, surveillance footage, or any other documents that are pertinent to the case.
Expert Reports: If the prosecution intends to call expert witnesses to testify, the defendant has the right to receive the expert reports detailing their findings and opinions. This allows the defense to prepare cross-examination and potentially challenge the expert's credibility or conclusions.
Prior Criminal Record: In most cases, the defendant may have the right to obtain information about the criminal record or prior convictions of prosecution witnesses. This can be relevant to assessing their credibility and potential biases. This is also needed to impeach a witness who says they have been the epitome of good behavior and never had so much as a parking ticket. It is the impeachment at trial that undermines credibility, not the type or seriousness of conviction - use of which is governed by the rules of evidence. Plus, knowing about cases that did not lead to conviction can reveal police reports in which a victim admits to lying (which this practice has seen). Defendants are also entitled to have their own record under constitutional law, case law, and statute.
Brady Material: Under the Brady rule in the United States, the prosecution must disclose any exculpatory evidence (which means evidence of innocence, diminished culpability, or evidence that would involve punishment) or evidence that could impeach the credibility of their witnesses. This includes evidence that is favorable to the defense, even if the prosecution believes it may not be ultimately useful for the defense's case. It should be noted too that even arrests or cases that do not lead to prosecution are important, as stated above.
The biggest confusion about discovery is Brady material, which takes its name from a famous case at the United States Supreme Court. When someone says something on the witness stand at trial that is inaccurate, incorrect, inconsistent, incomplete, misleading, or even an outright lie, a defendant (and the person acting for them - their attorney) is entitled to discovery that could challenge it there and then - to have that information to hand at that moment and to prepare for it before then. It is the process of challenging that lie or inaccuracy - however small - that challenges the witnesses credibility, not what the information in discovery contains. So, for instance, a person saying they have never been in trouble with the law or never even been arrested and who has been would be lying. It cannot stand. Without the ability to impeach the misstatement in that moment with prior discovery the trial becomes unfair. That information needs to be disclosed in discovery long before that moment. Discovery material that needs to be disclosed is NOT JUST is that someone is a liar. It is far far broader than that, but time and again this is not disclosed because it is unintentionally or deliberately misunderstood or too narrowly defined.
Pre-trial discovery is also much more extensive than when a conviction is challenged on an appeal - or at least it should be. Post conviction, the issue becomes whether the error is important enough for the guilty verdict to stand - known in legal jargon as 'materiality.' All important cases at the United States Supreme Court and Maine’s highest court are after a conviction. At that point the whole process switches to the default that the conviction is a good one. Prosecutors who do not disclose before a verdict are playing the game of whether the non disclosure is material. It’s a dangerous one to play because it can create the potential for miscarriages of justice. However, non-disclosure is far more common than everyone involved in the court system would care to admit - whether that is because prosecutors are swamped with cases, police officers do not give information about themselves (such as misconduct, adverse court rulings, etc) or evidence for the cases they bring because they too have a lot on their plate, or because those involved want to win.
The defense is sometimes also required to provide reciprocal discovery to the prosecution. This means that they must disclose certain information or evidence that they plan to use at trial, such as witness lists, expert reports, or alibi defenses.
The purpose of discovery is to promote a fair trial and prevent surprises during the proceedings. By providing defendants with access to relevant information, discovery helps ensure that they can present their case effectively and have a fair opportunity to challenge the charges against them, as well as eyewitnesses and even their accusers.
One important thing to note here. The touchstone about getting all discovery is fairness and due process. A defendant is the only party entitled to a fair trial. A prosecutor and the government is not. All rights and issues of fairness belong to the accused person - not an assistant district attorney, not the police, and not the witnesses for the prosecution. Governments don’t have rights, people do. To get a fair outcome, a defense attorney needs to be dogged, find evidence (often doing the work that should have been done because of a woeful police investigation), uncover discovery violations, and be unafraid to challenge the government.