Official term for “at large” or “on the loose”

When a convict is illegally out of prison – either escaped, or didn't get to the prison after his conviction – what is the right expression to describe this?

I want the term that is used in official documents, like court files, court orders, etc.

Solution 1:

In the UK, one is unlawfully at large.

 5. Unlawfully at large from prison
5.1. A prisoner is unlawfully at large when absent from prison, young offenders institute or remand centre as a result of:
* escaping or absconding from the prison establishment;
* failing to return to the prison establishment after a period of authorised temporary leave, or when the temporary leave has been revoked; or
* failing to return to prison after the revocation of a permanent licence or release, e.g. parole.

I have found a legislative reference: Prison Act 1952

Solution 2:

Definition of fugitive:

a person who has escaped from captivity or is in hiding:

fugitives from justice

According to a legal dictionary, a fugitive from justice is:

a person convicted or accused of a crime who hides from law enforcement in the state or flees across state lines to avoid arrest or punishment. Under Article IV, Section 2, Governors are required to "deliver up" and return any fugitive from justice to the state where they allegedly committed the crime, a process called extradition.