An amicus curiae (lit. “friend of the court”; pl. amici curiae) is a person or organization that is not a party to a court case, but has the right to assist a court by offering information, expertise or ideas that affect the problems of the case. Deciding whether or not to review an amicus letter is at the discretion of the court. The term is legal Latin and the origin of the term has been dated 1605-1615. The scope of amici curiae is usually found in cases where broad public interests are at stake and civil rights concerns are questioned.  Under Italian law, amici curiae are “non-profit organisations and institutional subjects, with collective or diffuse interests related to the question of constitutionality” which “may submit a written opinion to the Constitutional Court”.   In the United States, Amici Curiae usually files amicus briefs with appellate courts, although it is possible to file an amicus letter with the Federal District Court. The Amici can support a party or write neutrally in their pleadings. Amici advises and supports the courts in legal matters.
AMICI to draw the attention of the court to certain points of law that may have escaped the scrutiny of the court or the parties. The role of an amicus is limited to consultation, he cannot participate in the dispute as a party or lawyer of a party. In U.S. law, an amicus curiae generally refers to what is called an intervener in other jurisdictions: a person or organization that requests legislative proposals to provide a relevant alternative or additional perspective to the disputed issues. In U.S. courts, the amicus can be called the amicus letter. In other jurisdictions, such as Canada, an amicus curiae is a lawyer who is asked by the court to make legal submissions on matters that would not otherwise be properly disseminated, often because one or both parties are not represented by counsel. [Citation needed] Many companies choose to file an amicus letter if the outcome of the case directly affects their members. An amicus letter allows you to speak to the Court of Appeal about the matter at hand. You can inform the court of how a particular decision in the case affects your members and the organization to which you belong. They can also highlight the potential legal, economic or social implications of a particular judgment, including informing the court of the impact of a possible decision on an industry or on individuals or groups.
And an amicus letter may explain why a certain attitude of the court might not be feasible in other situations. They would do so to help the court understand the real consequences of a particular decision. An amicus curiae can usually only participate with the permission of the court, and most courts rarely allow people to appear as such. However, the U.S. Supreme Court allows federal, state, and local governments to express their views in all matters that concern them without the consent of the court or the parties. Persons may appear as amici curiae before the Supreme Court, either if both parties agree or if the court gives permission. State regulations on civil and appellate procedures regulate amici curiae in state affairs. Under Canadian law, an amicus curiae is a lawyer and not an external entity that is required by the court to provide opinions in a manner that ensures that legal issues affecting the interests of all parties are properly addressed.
If one of the parties (e.g. the defendant in criminal proceedings) is not represented (and is not eligible or refuses to apply for legal aid) and the judge fears that this party may be significantly disadvantaged and risk a miscarriage of justice, the judge may appoint a lawyer as amicus curiae. Counsel is not appointed by and does not represent the unrepresented party as such, but is responsible for ensuring that legal issues relevant to the party`s case are brought to the attention of the court. For example, in criminal proceedings, the amicus will be responsible for ensuring that the defendant`s right to a full answer and defence is preserved.