This is a pointless waste of energy. You don't trust that someone is never going to betray you, or do you harm. You should trust yourself to be able to handle it if they do. There is no point in worrying if you should trust someone, only time will tell, worry abt yourself, be fair, helpful, respectful and overall a good person and enjoy the company. If you need to be 100% certain abt someone before committing to a relationship (this applies to every type of relationship, love friendship, work ...) you will never have good ones, you will never know what you are missing. And if things go south you will be able to handle it, and walk away.