Okay let me preface this by saying that I am no lawyer.
However I learned one thing a long time ago...the law is like Count Dracula.
Now with those who are familiar with the movies, etc you will remember Dracula could never enter your house until you invited him in.
Now the same thing with the law.
You call the police and tell them your brother stole your computer and they recovered it. Well the computer is now states evidence and once in their possession they can do anything they wish with it.
That is why if you have anything bad remotely going on inside your pad i.e. a big bag of weed sitting out on the coffee table etc don't invite the cops in if they arrive at your front door.
A cop in most cases can only enter a premise if a call has been made and they believe a crime has been committed.
Now the next step is to get into your front door. Once inside your front door anything within sight is fair game...if they can see something from where they are that gives them probable cause to investigate further they can and will do so.
So once again the best thing to do is not to invite Count Dracula inside your house
then he can't suck your ass dry.
Now in your case I would find a lawyer and I would find one damn quick...do not answer anymore questions without a lawyer present.
And if they decide to pursue a case against you...well then man I do not know what to tell you but the fact that is that the computer was also in your brother's possession, you just might be able to deflect some of this off of you and onto him.