By 1848, the institution of Justice of the Peace in England and Wales had fallen into disrepute, its statutory basis dating back to the sixteenth century. Jervis was responsible for sponsoring, drafting and all-but single-handedly guiding through the House of Commons three bills to reform the criminal and civil roles of a Justice of the Peace in England and Wales:
- Indictable Offences Act 1848;
- Summary Jurisdiction Act 1848; and
- Justices Protection Act 1848.
The Acts won considerable praise as soon as they came into force though they did later attract criticism for their verbose style. In retrospect, Getzler expresses the opinion that the system of local justices would have fallen into further disrepute and ultimate decline and desuetude without these reforms. These Acts largely defined the modern system of summary and indictable offences within the Magistrates' Courts.
The first two Acts defined the duties of Justices acting other than at quarter sessions (
i.e. "out of sessions"). Jervis achieved consistency of practice by appending extensive forms and precedents to the Acts so as to provide a straightforward means by which Justices could comply though allowing them, at least the perception of, freedom to adapt to local circumstances. The prudent Justice followed the precedent and this was a tactic Jervis was to use again in the Common Law Procedure Acts.
The Indictable Offences Act is important in that it is the first codification of the police caution in England and Wales, in the words:
A fourth Act, the Petty Sessions Act 1849, proscribed the holding of petty sessions in "unsuitable" premises such as public houses, though it was delayed because the Bill's provisions as to salaries for magistrates' clerks and statutory scales for court fees proved unacceptable.