The generic Hebrew word for any kind of sin is avera (literally: transgression). Based on verses in the Hebrew Bible, Judaism describes three levels of sin. There are three categories of a person who commits an avera. The first one is someone who does an avera intentionally, or "B'mezid." This is the most serious category. The second is one who did an avera by accident. This is called "B'shogeg," and while the person is still responsible for their action it is considered less serious. The third category is someone who is a "Tinok Shenishba", which is a person who was raised in an environment that was assimilated or non-Jewish, and is not aware of the proper Jewish laws, or halacha. This person is not held accountable for his or her actions.
Pesha (deliberate sin; in modern Hebrew: crime) or Mered (lit.: rebellion) - An intentional sin; an action committed in deliberate defiance of God; (Strong's Concordance :H6588 (פשע pesha', peh'shah). According to Strong it comes from the root (:H6586); rebellion, transgression, trespass.
Avon (lit.: iniquity) - This is a sin of lust or uncontrollable emotion. It is a sin done knowingly, but not done to defy God; (Strong's Concordance :H5771 (avon, aw-vone). According to Strong it comes from the root (:H5753); meaning perversity, moral evil:--fault, iniquity, mischief.
Cheit - This is an unintentional sin, crime or fault. (Strong's Concordance :H2399 (חַטָּא chate). According to Strong it comes from the root khaw-taw (:H2398, H2403) meaning "to miss, to err from the mark (speaking of an archer), to sin, to stumble."
Cameron claims to be a Christian, so he must know the Bible reasonably well, as an educated man who is the Prime Minister of Britain.
He must have known about these verses at http://www.kingjamesbibleonline.org/Bible-Verses-About-Sodomy/
And even if he did not, in the same way he did not know what Magna Carta stood for, it would have been pointed out to him by those who opposed gay marriage.
An open and shut case then.
In Old Testament times I imagine such a man would be stoned to death.