The Perjury Act 1911 section 1 states that it is an offence if:
any person lawfully sworn as a witness or as an interpreter in a judicial proceedings wilfully makes a statement material in that proceeding, which he knows to be false or does not believe to be true, he shall be guilty of perjury, and shall, on conviction thereof on indictment, be liable to imprisonment for a term not exceeding seven years or to a fine or to both imprisonment and fine.
Perjury need not be limited to false oral evidence given in Court, but includes a false sworn document in connection with judicial proceedings or false evidence given before a tribunal.
The offence of perjury by its very nature, suggests that the defendant must be deliberately wilful, namely that he knows his evidence is false. The Courts have however clarified that the conduct is only wilful if it is deliberate or intentional and it must be proved that any perjury was not the result of a misunderstanding or a slip of the tongue.
The fact of whether a fact is material to a case is for the judge to decide. It is not necessary for the defendant to know or believe a fact is material. It is simply sufficent to show that the defedant knows of the falsity of his statement.