Peremptory challenges
Peremptory challenges, or challenges without cause, allowing the defence to prevent a certain number of jurors from serving without giving any reason, were formerly allowed in English courts and are still allowed in some other jurisdictions. At one time, the defence was allowed 25 such challenges, but this was reduced to 12 in 1925, to 7 in 1948 and 3 in 1977 before total abolition in 1988.[27][28]
Stand by
The prosecution and judge, but not the defence, have the right to prevent a juror from serving by asking them to "stand by". However, prosecutors are instructed to invoke this right sparingly as the quality of the jury is primarily the responsibility of the court officer. The right should only be invoked in cases of national security or terrorism, in which case the personal authority of the Attorney General is needed, or where a juror is "obviously unsuitable", and the defence agree.[29][30]
Challenge for cause
Either prosecution or defence can "challenge for cause" as many individual jurors as they wish on the grounds that the juror is:[31]
Ineligible or disqualified; or
Reasonably suspected of being biased.
These are the modern versions of the ancient challenges of propter honoris respectum, propter defectum and propter affectum.[31] Challenges have been successful where a juror was employed by or related to a party, had enjoyed entertainment at a party's home, or where they had already expressed an opinion on the case or shown hostility to the accused.[31] During the 1969 trial of the notorious gangsters, the Kray twins, the trial judge was prepared to exclude any juror who had read some of the current lurid newspaper reporting.[32] However, in a trial arising from the conduct of a picket in the bitterly contested UK miners' strike (1984–1985), a miner who had worked throughout the conflict was held to be fit to serve.[33]
http://en.wikipedia.org/wiki/Juries_in_England_and_Wales#Empanelling_and_challenging_jurorsI'd hope that a judge wouldn't count "do you know anyone with HIV" as "a reasonable suspicion of bias".
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