Police often need a search warrant if they cannot get your consent. They may use the warrant to search your computer or your house, for example. They often ask for consent, first. If you will not give your consent for a search, then they go to a judge and get a warrant.
One thing that you need to remember is that warrants should be not overly broad. They need to specifically lay out the terms for the search and limit themselves to only what is deemed necessary. For instance, a warrant should say that they can seize your personal computer from your office, not that they can seize all computers in your home.
Similarly, a search warrant for your house may specify areas of the home that can be searched. Police cannot overstep those bounds.
For instance, maybe you told them to get a warrant and come back when they asked to look in your attached garage. They left and came back with a warrant authorizing them to enter your home and search your garage. Once they’re inside, they can’t just use that warrant as free reign to look through the entire home, the attic and the basement. They can only look in the areas specified in the warrant.
What they may do is attempt to get your consent to search other areas once they’re in the garage. You do not have to provide it just because they have the initial warrant. You can still refuse and tell them to come back again with a new warrant for the rest of the house.
Do you think that police violated your rights by using an overly broad warrant or by stepping beyond the bounds of that warrant? You may be able to use that as part of your defense. When you’re facing criminal charges of any kind, it’s smart to protect your rights. Speak to an experienced attorney as soon as possible.