Consequence v Intention

There seem to be two ways or more to approach a problem.
When u determine a person's guilt, would u look at the consequence caused by his act ? or his intention?
Let say you are a judge, he done something that is not allow in the eye of society, either you also disagree with his act. Following his act, there is actually some unfavorable consequences which u have to decide whether he is guilt or not.
Nevertheless, when u look at the fact of the case-- his first intention actually not to cause the unfavourable consequence. He did it out of good intent, he never expect such bad thing will happen, but in fact it just happen. When he carried out his act, he actually din come across so many things.
how would u decide? convict or acquit?
forgive, or not?