The filing cabinets can be ransacked using the Thieving skill, requiring level 63 Thieving. Each successful attempt grants 75 Thieving experience (no experience is given when nothing interesting is found). The files are guarded by Level 54 Customs officers. Since players are not able to carry anything into the prison, the only weapon available are those looted, and Mithril scimitars dropped by the Customs officers. The only lootable weapon that surpasses the mithril scimitar the player is already wielding is the rune scimitar. Players also need to be wearing the Customs uniform: Customs hat, Customs shirt, and Customs trousers to enter the Evidence lockers room. Cabinets can be ransacked again after approximately 165 seconds (2min 45sec, depending on the server's player population) since the last time they were, although there are 17 of them in the room. It may be a good idea to lock the Customs officers in the little room in the north-eastern corner if the player does not wish to deal with them. (Note that this is only possible for three of them; one of the officers has a wander range too small for it to be locked in the office).
Note: The customs outfit and Mithril scimitar will always be lost when leaving the island.