Certain acts were once viewed as criminal, however since times have past the acts have been decriminalised . An example being sexual relationships with the same sex, it was criminal to be gay or lesbian. In 1967 the Sexual offences act dicriminalised homosexual acts between the same sex in private if persons were of 21 years of age.
Age of Responsibility
In England the age of criminal responsibility is 10 years old. This means that imprisonment/arrest/charging isnt an option. Other punishments are available e.g. youth offenders instituions.
If a child was to wonder into a shop and steal sweets this isnt a crime, however if an adult of 21 was to walk into a shop of steal alcohol they would be charged/arrested.
Certain crimes are given less sentences or none at all due to their specfic circumstances.
For example if a person injures someone in self defence then they will be treated differently if the attack would have been pure anger driven.
culture effects crime, as certain crimes are not seen to be criminal in certain culture. An example being bigamy, which is the act of marrying more than one eprson at once. This however is accepted in most western countires.