What would happen if there is an attempt by police to deceive a judge to get a warrant?
<p>Would I be correct in saying that police have a duty to fairly represent the facts to a judge when they attempt to get a warrant to search premises? Is there some sort of oversight in regard to how warrants are issued? Or is the oversight having your lawyer contest the validity of the search at your trial?</p>
<p>If a judge thinks the police are, either through neglect or incompetence, withholding information that would keep a judge from issuing a warrant what would happen then? Is this grounds for a policeperson losing his or her job or can a judge just then choose not to issue any further warrants with that department, making there job just that bit harder?</p>

<p>You are correct. A judge may only issue a warrant when it is supported by an affidavit, in which the officer seeking the warrant swears under oath to the facts supporting the warrant. Lying on the affidavit would constitute perjury.</p>
<p>But judges very frequently just rubber-stamp the warrants without meaningfully reviewing the affidavits, so the primary form of oversight would be the defendant's Fourth Amendment challenge asserting that the warrant wasn't supported by probable cause.</p>
<p>If a judge does review the warrant application and finds the officer's statements not to be credible, he can refuse to sign the warrant, and he is free to also carry that credibility determination to subsequent warrants sought by the same officer or other officers in his department.</p>

<p>Evidence obtained under a warrant supported by a falsely-sworn affidavit can be challenged as inadmissible, see <a href="https://supreme.justia.com/cases/federal/us/438/154/" rel="noreferrer">Franks v. Delaware</a>, 438 U.S. 154, if</p>
<blockquote>
<p>the defendant makes a substantial preliminary showing that a false
statement knowingly and intentionally, or with reckless disregard for
the truth, was included by the affiant in the warrant affidavit, and
if the allegedly false statement is necessary to the finding of
probable cause</p>
</blockquote>
<p>If the defendant makes a good case for an evidentiary hearing (the court says more specifically what that means), and</p>
<blockquote>
<p>after a hearing, a defendant establishes by a preponderance of the
evidence that the false statement was included in the affidavit by the
affiant knowingly and intentionally, or with reckless disregard for
the truth, and the false statement was necessary to the finding of
probable cause, then the search warrant must be voided, and the fruits
of the search excluded from the trial to the same extent as if
probable cause was lacking on the face of the affidavit</p>
</blockquote>
<p>So even if the warrant is signed, it can be invalidated.</p>

<p>You are correct that the defendant's lawyer is the main protection against this kind of thing. The lawyer will file a motion to suppress the evidence based on lack of probable cause. If successful, the evidence can't be used at trial and the prosecutor will probably have to drop the charges unless they have or can come up with some other evidence.</p>
<p>Also note that under <a href="https://supreme.justia.com/cases/federal/us/468/897/" rel="noreferrer">Leon</a> the trial court is generally going to show deference to the magistrate judge's decision re granting the warrant. But if there is deception on the part of the officer the trial court will no longer show deference. That means there is a much better chance of winning on your motion to suppress than you'd have in a case without deception.</p>

united-states search-and-seizure criminal-procedure fourth-amendment