Sworn testimony is evidence given by a witness who has made a commitment to tell the truth. If the witness is later found to have lied whilst bound by the commitment, they can often be charged with the crime of perjury

Perjury

Perjury, also known as forswearing, is the willful act of swearing a false oath or affirmation to tell the truth, whether spoken or in writing, concerning matters material to a judicial proceeding. That is, the witness falsely promises to tell the truth about matters which affect the outcome of the...

. The types of commitment can include oaths, affirmations and promises which are explained in more detail below. The exact wording of the commitments vary from country to country.

Types of commitment

The commitment can come in different forms depending on the situation of the witness. The types of commitment used in the United Kingdom

United Kingdom

The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

 are:

• Oath: A commitment made to the witness's deity
  Deity
  A deity is a recognized preternatural or supernatural immortal being, who may be thought of as holy, divine, or sacred, held in high regard, and respected by believers....
  
  , or on their holy book.
• Affirmation: A secular
  Secularism
  Secularism is the principle of separation between government institutions and the persons mandated to represent the State from religious institutions and religious dignitaries...
  
   variant of the oath where the witness does not have to mention a deity or holy book.
• Promise: A commitment made by a witness under the age of 17, or of all witnesses if none of the accused are over the age of 17.

South Africa

Oath:

I swear that the evidence that I shall give, shall be the truth, the whole truth and nothing but the truth, so help me God.

Affirmation:

I solemnly affirm that the evidence that I shall give, shall be the truth, the whole truth and nothing but the truth.

England and Wales

England and Wales

England and Wales is a jurisdiction within the United Kingdom. It consists of England and Wales, two of the four countries of the United Kingdom...

Oath:

I swear by [substitute Almighty God/Name of God (such as Allah

Allah

Allah is a word for God used in the context of Islam. In Arabic, the word means simply "God". It is used primarily by Muslims and Bahá'ís, and often, albeit not exclusively, used by Arabic-speaking Eastern Catholic Christians, Maltese Roman Catholics, Eastern Orthodox Christians, Mizrahi Jews and...

) or the name of the holy scripture] that the evidence I shall give shall be the truth, the whole truth and nothing but the truth.

Affirmation

I do solemnly and sincerely and truly declare and affirm that the evidence I shall give shall be the truth, the whole truth and nothing but the truth.

Promise

I promise before Almighty God that the evidence which I shall give shall be the truth, the whole truth, and nothing but the truth. http://www.opsi.gov.uk/si/si1997/97017211.htm

Scotland

Scotland

Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...

Oath:

I swear by Almighty God that I will tell the truth, the whole truth and nothing but the truth. http://www.opsi.gov.uk/legislation/scotland/ssi2002/20020132.htm

Affirmation:

I solemnly, sincerely and truly declare and affirm that I will tell the truth, the whole truth and nothing but the truth.

Sources

• Judicial Studies Board (of England and Wales)