Juries - challenges

Challenge for cause - by defence or prosecution.
Challenge; show good cause	When a jury has been empanelled, but before the jurors are sworn, the defendant has a right to object to any one or more jurors if he can (for example, that the juror knows him). A challenge for cause may be made by either the prosecution or defence. It is either a challenge to the whole panel of jurors or to an individual juror. The former is known as a challenge 'to the array' and the latter as a challenge 'to the polls'.
Challenge 'to the array'
Bias or impropriety	The usual ground was that the person responsible for summoning the jurors in question is biased or has acted improperly, Bias or impropriety on the part of the summoning officer has ceased to be a live problem, particularly as it is done by computer.
Racial or other imbalance.	There are no grounds for challenging a jury panel which is imbalanced racially or not reflecting the overall racial composition of the catchment area from which jurors are summoned is not sufficient ground for challenge (Danvers [1982] and Broderick [1970] and Ford [1989]. The principle of these decisions will apply equally to other imbalances for example all women or all men on the jury or an imbalance in sex.
Challenge to the polls
Presumed or actual bias	Some presumed or actual bias which would make him unsuitable to try the case are grounds for a challenge. It may be that a juror has expressed hostility to one side or the other or has expressed a wish as to the outcome of the case, is related to a party, or has some other connection with a party, for example an employer or employee. The issue of newspaper reporting of cases was effectively dealt with by Kray (1969)
No jury quizzing	Challenge for cause is very limited, because no questioning of jurors to establish a cause is normally allowed, and only the most obvious bias is likely to be detected. This is completely different from other jurisdictions, for example the USA where extensive quizzing of jurors occurs, see jury vetting, below.
Stand by - by the prosecution.
"Stand by for the Crown"	The prosecutor too may challenge for cause, and may also ask a juror to "stand by for the Crown" (to serve only if no other juror is available), but this power is very rarely exercised except in cases affecting State security. Standing a juror by differs from challenging him for cause in that no reason has to be given. It also differs because the juror is not conclusively removed from the jury but will be recalled to the jury-box should the entire jury panel be exhausted without a full jury being obtained, at which stage the prosecution must either accept him or show cause why he should not serve.
Reasons for stand by	The Crown might properly exercise its right to stand by a member of a jury panel because: jury checks reveals information justifying exercise of the right; or a person is about to be sworn as a juror is manifestly unsuitable and the defence agree. For example, a juror selected for service to try a complex case is in fact illiterate. The right is exercised only in the tiny minority of cases which involve national security or terrorism or 'ordinary' cases where a juror is obviously unsuitable and the defence agree, or they are in fact disqualified by previous convictions, or they know the accused or any witnesses in the case, or bias; if a juror's previous convictions (which do not disqualify him) or other involvement with the police might make him so prejudiced against the Crown as to be unable to try the case fairly. Whether such a challenge would succeed is open to question.
Intervention by the judge	Where an individual juror is obviously incompetent to act but, for whatever reason, counsel do not challenge or exercise the right of stand-by it is the judge's duty to prevent the 'scandal and perversion of justice which would arise from compelling or permitting such a juryman to be sworn' (per Lord Campbell CJ in Mansell. Examples for the judge's intervention include the juror was mentally or physically infirm, or insane or drunk, or preoccupied with the dangerous illness of a relative. A judge may notice that a member of the panel is infirm or has difficulty in reading or hearing; and nowadays jurors for whom taking part in a long trial would be unusually burdensome are often excluded from the jury by the judge.
What the judge will say	The Judicial Studies Board has produced model directions that a judge should give a jury, and how to decide on "challenges", reproduced here.