The nature of sacrifice seems to confuse a lot of people. It is true that animal sacrifices were once considered (in both Pagan and Christian cultures) to be an acceptable offering to the Gods. But what you need to remember is that back in olden times people had very few possessions and their livestock would be one of the most valuable things that they owned. The power of sacrifice is not the spilling of blood or the ending of life, it is the act of giving something up that means something to the person doing the sacrifice. It follows that in olden times slaughtering a goat or a chicken would have been a genuine sacrifice – in modern times killing random animals has little meaning or significance attached to it.
Do witches perform sacrifice? Certainly I do – but I assure you that my hands do not become in the least bloody when I do so. I perform sacrifice that actually involves me losing something - sacrifice by direct debit rather than by death. Generally when I wish to either thank the Gods or ask them for something I try to put something into the world to do some good, like a donation of money to charity. A fellow witch thanks the universe by putting things back into the earth, planting seeds that sort of thing. These positive actions are to my mind far more acceptable sacrifices than a meaningless act of random destruction such as the killing of an innocent animal.
You seem a little confused about witches and the Devil. Very few witches believe in or worship the Devil. Devil worship is more akin to Satanism. And I have to be honest, I know a few Satanists and they would be far more outspoken than me on the subject of killing random cats. They’d call you an idiot and quite rightly so. No self respecting Satanist goes around stealing cats off old ladies. It is hardly surprising that two teenage boys and a dead cat failed to raise a demon of any sort. I can’t deny there are certain rites that do involve blood ritual but without knowing what you are doing, you are unlikely to get very far. I’d also question what exactly you intended to do with the demon in the unlikely event that you had managed to summon anything. Magic without a motive or a direction is nothing but posturing. If you genuinely feel called to a magic path, start with the basics, learn your craft from the bottom up and stop trying to impress your friends with things of which you have no understanding.
Do I think killing a cat is forgivable? Yes, suppose I do (though I do not condone such unnecessary violence and to my mind only a weak person hurts animals) - But I am of the firm belief that we all make mistakes and we all do stupid things occasionally and I do not feel that the rest of your life should be tainted with the guilt of one adolescent incident. I’d suggest that you take some positive steps to apologise for your action – I’m not keen on all this saying sorry and being forgiven business – if you want to feel you can put the incident behind you, go out of your way to atone for it. Give some money or time to a cat charity, help out some elderly neighbours, volunteer at a cat rescue place….Whatever… but do something positive to help others and offer up the gift of that sacrifice to the Gods.
Image http://www.sxc.hu/photo/1425719 (wrhoanaz)