Julie Jonas, a professor at the University of St. Thomas School of Law, spoke with WCCO-TV about how law enforcement obtains search warrants and the legal requirements involved in their approval. Jonas explained how investigators establish probable cause, the limits placed on searches and why judges rarely reject warrant applications.

From the story:
Despite the heavy scrutiny, judges rarely deny warrant applications. A study analyzed 33,000 warrant applications over three years in Utah. It found 98% eventually were approved and 93% were approved on the first submission. That approval rate didn’t surprise Jonas.
“There’s no requirement on how much time the judge spends reading law enforcement’s affidavit or that the judge does any individual investigation, him or herself,” she said. “I think they tend to believe law enforcement has done its job; they’ve investigated this case as far as they can without searching this person’s home, now we’re going to give a great deal of deference to law and enforcement.”
If a search warrant application is denied, Jonas says it’s usually because witness statements, especially from confidential informants, weren’t properly verified.
Once law enforcement submits the application, the potential approval comes back quickly.
“There are judges on call 24/7, so law enforcement goes in with an affidavit and the warrant is issued very, very quickly to that same officer who can then go execute it,” Jonas said.