Mentioning two or more defendants in one count of an indictment and trying them together. It is possible to join two or more defendants even if one of them is the principal offender and the other an accessory; if they are separately indicted, however, they cannot subsequently be tried together. Sometimes (e.g. in cases of conspiracy) it is usual to join two or more defendants; one may be convicted even if all his co-conspirators named in the count are acquitted and even though conspiracy by definition requires more than one participant. Two or more defendants may also be joined in one indictment if they are charged with different offences, if the interests of justice require this; for example, if two witnesses commit perjury in relation to the same facts in the same proceedings. Defendants who have been jointly indicted will normally only be tried by separate trials if a joint trial might prejudice one or more of them; for example, when evidence against one accused is not admissible against the other or when the prosecution wish to call one of the defendants to give evidence against another.