. (2) However, if the law in force at the time of conviction is different from the law in force at the time of the commission of the offence, the new law applies if its application leads to a more lenient result. (3) If the law is intended to be in force only for a fixed period of time, and there are no provisions to the contrary, the law in force at the time of the commission of the act applies to an act committed during this period. (4) If the specific contents of a penal provision in law are determined by other provisions in law or by provisions or rules issued on its basis, the punishability of an act is assessed on the basis of the provisions or rules in force at the time of the act, unless there are provisions in law to the contrary or unless the new provisions demonstrate that the attitude towards the punishability of the act has changed. Section 3 – The punishability of omission (515/2003) (1) An omission is punishable if this is specifically provided in the statutory definition of an offence. (2) An omission is punishable also if the offender has neglected to prevent the causing of a consequence that accords with the statutory definition, even though he or she had had a special legal duty to prevent the causing of the consequence. Such a duty may be based on: (1) an office, function or position, (2) the relationship between the offender and the victim, (3) the assumption of an assignment or a contract, (4) the action of the offender in creating danger, or (5) another reason comparable to these. Section 4 – The age of criminal liability and criminal responsibility (515/2003) (1) Prerequisites for criminal liability are that the perpetrator had reached the age of fifteen years at the time of the act and is criminally responsible. (2) The perpetrator is not criminally responsible if at the time of the act, due to mental illness, severe mental deficiency or a serious mental disturbance or a serious disturbance of consciousness, he or she is not able to understand the factual nature or unlawfulness of his or her act or his or her ability to control his or her behaviour is decisively weakened due to such a reason (criminal irresponsibility). (3) If the perpetrator is not criminally irresponsible pursuant to subsection 2 but, due to mental illness, mental deficiency, mental disturbance or disturbance of consciousness, his or her ability to understand the factual nature or unlawfulness of his or her act or his or her ability to control his or her behaviour is significantly weakened (diminished responsibility), the provisions in Chapter 6, section 8(3) and 8(4) are to be taken into account in the determination of the sentence.