Legal Question in Constitutional Law in Texas

Re: Search of a Locked Box

Ordinarily, giving permission to search a car conveys permission to search any container within the car, regardless of whether it is locked.

Refusing to allow the officer to search the box does not entitle him to search it (if the law worked this way, officers could search any place they want at any time, since they would either get permission or would be authorized by the denial of permission), but your question presumes that the officer never had such authority in the first place. The reason he was authorized to look inside the box is that you had already given permission to search the car and not that you tried to prevent him from seeing what the box contained.

By the same token, a routine traffic infraction would not be enough to authorize a search against the driver's wishes.

You can still argue that whatever evidence the police found inside the box was obtained illegally and that it must be thrown out, but I don't think your argument is likely to succeed. The fact that the officer had to use force to open it is beside the point, since the situation would be no different had he simply been able to pick the lock.

If you are going to make this kind of argument, you really should have a lawyer working for you. A successful motion to exclude evidence must usually discuss numerous precedents and explain why they support the defendant's position. This is something lawyers are trained to do, but which most laypeople are ill-prepared to attempt.