If you have ever considered placing a GPS tracker on a vehicle to find out where someone is going, you need to read this before you do anything. This comes up most often in infidelity cases — if that is your situation, also read Infidelity Investigations: What to Expect for a full picture of how a licensed PI gathers evidence legally.
Illinois law is unambiguous on this point. Secret GPS tracking is a criminal offense. It does not matter if you are married to the person. It does not matter if you own the car. In most situations, placing a hidden tracker without consent exposes you to criminal charges, civil liability, and the very real possibility that any evidence you gather will be used against you rather than for you.
Here is what the law actually says — and how a licensed private investigator gathers location evidence the right way.
The Unauthorized Tracking Device Act (720 ILCS 5/21-2.5)
Illinois enacted the Unauthorized Tracking Device Act specifically to address the growing use of electronic tracking devices — GPS units, AirTags, Tile trackers, and similar technology — to monitor people without their knowledge.
Under the statute, secretly placing an electronic tracking device on a vehicle is a Class A misdemeanor, punishable by up to one year in jail. The law applies to any electronic device capable of recording or transmitting location data. That includes consumer products like Apple AirTags, which have been at the center of numerous stalking cases in Illinois and nationally.
No Marital or Relationship Exception
This is the part that surprises most people.
Being married to someone does not give you the legal right to secretly track them. A spouse has no more legal authority to place a hidden GPS device on their partner's vehicle than a stranger does. Illinois courts have not recognized a marital exception to this statute, and law enforcement treats violations the same regardless of the relationship between the parties.
The same applies to dating relationships. A boyfriend or girlfriend has no legal right to secretly track their partner.
The Vehicle Ownership Exception — and Its Limits
The statute does contain one notable exception related to vehicle ownership.
The law states that consent by the registered owner or lessee of a vehicle constitutes consent for any other driver of that vehicle. In practical terms: if a husband is the sole registered owner of a vehicle his wife drives, placing a tracker on that vehicle may technically fall outside the specific Unauthorized Tracking Device Act.
However, this exception is narrow and carries serious risks:
- If the partner is the registered owner, secret tracking remains illegal.
- If the vehicle is jointly owned or jointly leased, secret tracking remains illegal.
- Even where the ownership exception applies to the tracking device statute, the conduct can still trigger criminal charges under Illinois stalking and cyberstalking laws.
Escalation to Stalking and Cyberstalking Charges
This is where the ownership exception can collapse entirely.
Even if a person legally owns the vehicle and uses the ownership exception to place a tracker, doing so without the driver's knowledge can still result in criminal charges under Illinois Stalking (720 ILCS 5/12-7.3) and Cyberstalking (720 ILCS 5/12-7.5) laws.
If the unauthorized tracking causes the subject to fear for their safety or suffer emotional distress, it can be prosecuted as a Class 4 felony — carrying a potential sentence of one to three years in prison. That is a significant escalation from a misdemeanor, and it applies even when the tracker was placed on a vehicle the person owns.
Civil Consequences
The criminal exposure is only part of the picture.
A person who discovers a hidden tracker can obtain an Order of Protection, which carries immediate arrest upon violation. They can also sue in civil court under the tort of Intrusion Upon Seclusion — a recognized cause of action in Illinois that allows recovery of damages for unauthorized invasion of a person's private affairs.
In a divorce or custody proceeding, the discovery of a hidden tracker can shift the entire dynamic of the case — against the person who placed it.
What About Using GPS Evidence in Divorce Court?
Illinois is a no-fault divorce state. Courts do not require proof of infidelity to grant a divorce, and fault-based conduct generally does not affect property division or maintenance (alimony) awards.
More importantly: evidence gathered through an illegally placed tracking device is subject to exclusion and will not favorably impact your case. Courts routinely sanction parties who attempt to introduce illegally obtained surveillance data, and the conduct itself — placing the tracker — can be used against you. The risk is not just that the evidence gets thrown out. It is that you become the person who broke the law.
How a Licensed PI Gathers Location Evidence Legally
There is a legal, court-admissible way to document where someone has been — and it does not involve placing anything on anyone's vehicle.
License Plate Recognition (LPR) Data
Through professional investigative databases like IRBsearch, I can access nationwide LPR data — time- and date-stamped vehicle sighting records captured by cameras mounted on police vehicles, repossession trucks, parking enforcement units, and fixed infrastructure across the country.
If a subject's vehicle has been consistently appearing at a specific address, LPR data can document that pattern without any physical contact with the vehicle. No tracker. No trespass. No criminal exposure. The data is generated by third-party systems and is suitable for use in legal proceedings.
This is particularly effective in alimony cohabitation cases, where documenting consistent vehicle presence at a shared residence is often the key piece of evidence.
Field Surveillance
Covert mobile and stationary surveillance conducted from public spaces is entirely legal in Illinois. A licensed PI can document a subject's movements, meetings, and activities through direct observation and photography or video — all without placing any device on any vehicle.
The resulting evidence is legally obtained, properly documented, and admissible in court.
Database and Records Research
Skip tracing, address history, associate networks, and public records searches can establish location patterns and connections without any physical surveillance at all. These tools are available to licensed investigators through professional databases that are not accessible to the general public.
The Bottom Line
If you are considering placing a GPS tracker on someone's vehicle — even your spouse's, even a car you own — stop and call a licensed PI first.
The legal exposure is real. The risk that your evidence gets thrown out is real. And the risk that you become the defendant in a criminal or civil proceeding is real.
There is a legal way to get the location evidence you need. In alimony and cohabitation cases, LPR technology can document a vehicle's location history without anyone touching the car — read the LPR Case Study to see exactly how it works. For spousal maintenance cases specifically, see Illinois Alimony Laws and Cohabitation. It starts with a free, confidential consultation.
P.I. Radames — Illinois PI License No. 115-002640 Call or message to discuss your case. Everything is confidential.
