What process entails obtaining a witness' presence at a trial by court order?

The process of obtaining a witness' presence at a trial through a court order is known as a subpoena. A subpoena is a legal document that commands an individual to appear at a specified time and place to provide testimony or produce evidence in a legal proceeding. This mechanism is essential in the judicial system, as it ensures that crucial witnesses can be legally compelled to participate in trials, thereby contributing to the pursuit of justice.

The other terms provided are part of the legal process but serve different functions. An affidavit is a sworn written statement used as evidence, rather than a method for summoning individuals to court. Discovery refers to the pre-trial phase where parties exchange information relevant to the case, but it does not involve compelling witnesses to appear. Interrogatories are a form of written questions sent from one party to another in a lawsuit to gather information, rather than a process for ensuring a witness's attendance at a trial.