The term "blood on his hands" is not a legal concept. It is a guiding principle determined on a somewhat ad hoc basis by the Shin Bet (Israel Security Agency), and is the result of the reciprocal relations between the government and the public. In other words, aware of the understandable ambivalence of large sections of the public to the lopsided prisoner exchanges that have become routine between Israel and its enemies, the government has declared that no matter how many prisoners it releases, it will not release the "worst" terrorists, that is, one "with blood on his hands." The Shin Bet established the criteria for determining which terrorist has blood on his hands, and it was incorporated into a cabinet decision in 2003. Since then, every government decision to release prisoners has referred to the criteria included in that decision. According to these criteria, a terrorist who does not literally spill blood - as hard or as often as he may try - is not classified as having blood on his hands, even if he is sentenced to 10 years in prison. On the other hand, a youth who throws a rock and draws blood from a victim, no matter how superficial the wound, is considered to have blood on his hands, even if he is sentenced to only eight months. The hardened terrorist will be released unless there is some special reason to hold him, while the youth will be kept in jail. According to attorney Emi Palmor, head of the Justice Ministry's Pardons Department, not only those who actually spill blood are considered terrorists with blood on their hands, but also the outer circles that helped them along the way, such as the planners of the attack, the drivers who bring the terrorists to the scene of the attack, and so on. The Pardons Department has a computerized data basis that includes details on every prisoner in the country - both criminal and security. The data is updated on a daily basis. The department is able to obtain lists of prisoners according to various criteria, including which are security prisoners and which are criminal, how much of their sentence has been completed, etc. After the various lists have been selected, an interministerial committee, headed by the Justice Ministry director-general and including representatives of the various security branches, goes over the list to determine which of those appearing on it should not be released for special reasons based on intelligence information. This winnowing-out process has created situations where the number of prisoners is less than the number the government has promised. In such cases, it may soften the definition so that those who technically have blood on their hands but are relatively distanced from the actual attack may be released. It does so reluctantly, however, and would prefer to release a prisoner who has only served a small fraction of his sentence, rather than one with blood on his hands, even if the latter has served most of his sentence.