Some technical stuff here:
A coroner's jury is only necessary in a limited number of inquest cases, as in the majority of cases the coroner sits alone. The number of jurors is a minimum of seven and a maximum of eleven. The four categories of case where a coroner's jury is currently required are set out in the Coroners Act, 1988, s 8(3). In broad terms, they are where it appears to the coroner that there is reason to suspect a death
(1) in prison;
(2) in police custody or as a result of police causing injury;
(3) which is reportable under separate legislation to a government department or officer or to the HSE;
(4) occurring in circumstances prejudicial to public health or safety.
The coroner also has power to sit with a jury in any other case where it appears to him that there is reason to do so. In practice, this is rare. Under the Coroners Act 1988 s 9, persons are qualified to sit as coroner's jurors only if they are qualified to sit as jurors in the Crown Court, the High Court and the county courts, and are not otherwise disqualified. The qualification is set out in the Juries Act 1974, s 1, has been significantly amended by the Criminal Justice Act 2003, s 321 and Sch 33, as from 5 April 2004, by virtue of SI 2004 No 829. The proposals (before they were enacted) were summarised in the Home Office Newsletter to Coroners No 41, dated 28 April 2003, para 4. The rules on excusal from service on the coroner's jury have also been amended, by SI 2004 No 921.