Probable cause to believe a person committed an offense does not necessarily answer a separate and critical question: why should police expect evidence of that offense to be found in the particular home, vehicle, cellphone, account, container, or other place they want to search?
The search-warrant affidavit should establish the legally required connection—or nexus—between the suspected evidence and the particular place to be searched. This connection is as important to warrant validity as the probable cause underlying the suspected criminal activity.
Probable Cause Has to Point Somewhere
A search warrant does not authorize police to search everywhere associated with a suspected person. The warrant authorizes a search of a particular place or thing.
The affidavit therefore should do more than describe suspected criminal conduct. It should provide a factual basis for believing evidence connected to that conduct will probably be found in the particular location officers seek authority to search.
This connects directly to the Criminal Defense Library article "Probable Cause and the Search-Warrant Affidavit: What Did the Judge Actually Know?", which examines the foundation upon which probable cause determinations rest.
What Is Nexus?
Nexus is simply the connection between the suspected criminal activity, the evidence police seek, and the particular place or thing police want permission to search.
Nexus should not be treated as a technical vocabulary exercise. The practical question is straightforward:
Why did police believe the evidence would be there?
The answer might rest upon direct observations, information from witnesses or informants, surveillance, reasonable inferences about where a particular type of evidence is ordinarily kept, or other factual circumstances. Whatever the basis, the affidavit should establish the connection.
Suspicion About a Person Is Not Automatically Suspicion About Every Place Connected to That Person
This principle is crucial for accurate warrant analysis. Probable cause involving an individual does not necessarily establish probable cause to search every residence, vehicle, device, account, or property associated with that individual.
An affidavit might establish that a person is suspected of drug trafficking without necessarily establishing that a search of that person's mother's home, a borrowed vehicle, a work-related account, or a third party's property is warranted.
The affidavit should provide the legally sufficient factual connection required for the particular search requested. Categorical statements are unhelpful because the permissible inferences depend upon the facts, the nature of the alleged offense, the type of evidence sought, and applicable law.
Searching a Residence
When police seek authority to search a home, the nexus question becomes especially important because homes receive strong Fourth Amendment protection.
The affidavit should address:
What evidence are officers looking for? Why do they believe it is inside this residence? What connects the accused person to the residence? What recent observations concern that location? Did surveillance show relevant activity? Did a witness or informant report seeing evidence there? Are officers relying upon an inference about where a particular type of evidence is normally kept? What facts support that inference in this particular investigation?
The defense should identify precisely how the affidavit connects the alleged crime and evidence to the residence. General suspicion that an individual committed an offense is not necessarily sufficient to justify searching the individual's residence.
Searching a Vehicle
Similar nexus questions arise when police seek authority to search a vehicle.
The defense should examine:
Who owns or controls the vehicle? Who was using it? When did it allegedly become connected to the investigation? What did officers observe? What evidence is supposedly inside? Why do officers believe the evidence remained there at the relevant time?
The existence of a relationship between a person and a vehicle does not eliminate the need to analyze the factual basis for the search. A vehicle registered to a particular individual might belong to someone else or might be used by multiple people. The affidavit should establish why a search of the specific vehicle is justified.
Cellphones and Digital Devices
Digital searches make nexus particularly important because phones and devices can contain enormous amounts of personal, business, financial, health, communications, and other sensitive information.
When police seek authority to search a device, the affidavit should address:
What evidence are investigators seeking? Why do they believe this device contains it? What connects the device to the alleged conduct? Who allegedly used or controlled the device? What time period is relevant?
Digital-search scope and particularity present additional issues beyond nexus that will receive separate treatment in the Criminal Defense Library. The point here is that the affidavit should establish the connection between the device and the alleged evidence.
Accounts, Messages, and Cloud Data
Similar nexus analysis applies when police seek electronic communications, account records, location information, photographs, stored files, or other digital evidence.
Whether seeking email, social media accounts, messaging platforms, cloud storage, financial accounts, or other digital sources, the affidavit should establish what connects the particular account or source of data to the alleged offense and to the particular evidence investigators seek.
Electronic warrants and digital searches present issues extending beyond nexus alone. This article focuses on the foundational question: why should police expect the evidence to be found in this particular digital location?
What Facts Create the Connection?
Nexus may be based upon various facts and reasonable inferences, depending upon the case.
Potential sources creating the connection may include:
Officer observations; surveillance; witness statements; confidential-informant information; admissions or statements by the suspect; photographs or video; communications; location information; transactions; records; patterns of conduct; or reasonable inferences drawn from the nature of the alleged activity.
The defense should identify which facts actually appear in the affidavit and which conclusions investigators ask the magistrate to draw from them. Understanding the evidentiary basis for the nexus assertion is essential to evaluating whether it establishes the necessary connection.
Facts, Inferences, and Assumptions Are Not the Same Thing
A strong analytical approach breaks the affidavit into three distinct questions:
First: What facts are actually alleged in the affidavit? Second: What inference does the government ask the magistrate to draw from those facts? Third: What conclusion does that inference supposedly support about why the evidence will be found in the place to be searched?
Reasonable inferences may legitimately contribute to probable cause and nexus. The defense nevertheless should identify where factual allegations end and inferential reasoning begins. A chain of inferences is weaker than direct facts. An assumption is weaker still. The affidavit should ground nexus in facts and reasonable inferences rather than assumptions or speculative theories.
Timing and Nexus Work Together
Even a factual connection to a location may need to be evaluated in light of timing. If evidence was reportedly present at a location days, weeks, or months earlier, the defense should ask why officers believed the evidence would still be there when the warrant was requested.
The answer may depend upon:
The type of evidence; the nature and duration of the alleged activity; whether the evidence is consumable (like drugs), movable (like a vehicle), durable, digital, or likely to be retained; and other circumstances specific to the case.
A connection established by months-old observations may have become stale. The concept of staleness—when information becomes too distant in time to justify relying upon it—will be addressed in a separate Criminal Defense Library article. Here, understand that nexus and timing work together to establish whether evidence will probably be found at the location at the time the warrant was issued.
Compare the Nexus Allegations With the Discovery
The defense may compare the affidavit's asserted connection with available discovery, including:
Body-camera footage; surveillance video; photographs; police reports; witness interviews; dispatch records; digital records; location information where available; property or vehicle records; communications; and other relevant discovery.
Ask whether the underlying evidence actually supports the factual connection described in the affidavit. Do observations shown on body-camera actually match the officer's description? Was the property accessible and controlled as the affidavit suggests? Did the suspect actually demonstrate access or ownership?
Discrepancies do not automatically invalidate a warrant but may identify issues requiring further investigation or examination during litigation.
The Place to Be Searched Matters as Much as the Crime Alleged
Warrant analysis should not focus exclusively upon whether investigators had evidence of criminal activity.
A second question is equally important:
Why did that evidence justify searching this particular place?
A strong suspicion that a crime occurred and a legally sufficient basis to search a particular location are related questions, but they are not necessarily identical questions. The defense should ensure that warrant review includes careful examination of nexus—the connection between the suspected evidence and the specific place police want authority to search.
Ask the Simple Question: Why There?
When reviewing a search-warrant affidavit, the defense should ask a deceptively simple question:
What evidence are police looking for? Why do they believe that evidence exists? Why do they believe it is in this particular place? What facts create that connection? How recent are those facts? Are officers relying upon direct observations, information from others, reasonable inferences, or assumptions? Does the affidavit actually explain the connection?
Probable cause does not exist in the abstract. It must connect to something—a place, a person, an activity, a location. When police ask for authority to search a particular place, the defense should examine why the government says the evidence will be found there. Nexus is the bridge connecting probable cause to the search location. If the bridge is weak, the warrant's foundation is weak.