At the heart of whether President Clinton committed perjury is the definition of what constitutes sexual relations. A definition was agreed by the President's lawyers and the legal team of Ms Paula Jones in the sexual harassment case taken against him by Ms Jones.
According to this definition, sexual relations are established when a person "knowingly engages in or causes . . . contact with the genitalia, anus, groin, breast, inner thigh, or buttocks of any person with an intent to arouse or gratify the sexual desire of any person". Contact was agreed to mean intentional touching, either directly or through clothing.
In his deposition in the civil action brought by Ms Jones, Mr Clinton denied having had sexual relations with her. In subsequent testimony under oath to the grand jury in the Starr investigation, Mr Clinton, using the Jones case definition, denied having had sexual relations with Ms Monica Lewinsky.
The question as to whether oral sex falls within or outside the Jones definition of sexual relations - and the President's lawyers contend that it is outside - will be central to any consideration of whether he committed perjury.