The ICC Office of the Prosecutor (OTP) may turn a preliminary examination into a formal investigation called a situation (such as, the situation in Libya) if the four phases of a preliminary examination are satisfied.

In an investigation, the OTP gathers as much information as possible to construct an accurate interpretation of the events of the alleged crime as well as to determine who is most responsible. An investigation may include:

• Inspection where the alleged crimes occurred;
• Collection of evidence like documents and forensic material;
• Interview witnesses and victims;
• Consultation with relevant experts and specialists;
• Analysis of financial transactions; and
• Use of modern technologies (such as data analysis) to uncover additional evidence.

The OTP is legally required to gather all evidence, including incriminating and exonerating evidence. All evidence must be given to the Defense in a process called disclosure.