DUI-DWI cases are rarely based on physical evidence that has been taken from you in an illegal search
It is a very rare DUI-DWI case that revolves around physical evidence that has been taken from you by the government in an unlawful manner. Most DUI-DWI cases revolve around the officer's testimony as to what he or she observed, video tapes or audio recordings made by the officer in the line of duty, and physiological testing (blood, breath or urine) performed on you to establish the presence and quantity of alcohol or drugs in your system at the time of your arrest.
The Fourth Amendment protects you from illegal searches by the police
Unless you are arrested, or willingly consent to a search, you have the Fourth Amendment protection against an unlawful search of you or your vehicle. The police cannot delay you too long before they either have to arrest you, or let you go. Furthermore, having a dog sniff your vehicle while it is stopped, as long as it does not delay the process of you being ticketed, is not an illegal search. This is why you should never have ANY illegal drugs in your vehicle, in case your routine speeding ticket is being issued by an officer who just happens to have a drug-sniffing dog in his or her vehicle.
Examples of Illegal Searches
Being placed in the back of a police car before being "officially" arrested, and then waiting until another officer arrives to perform your field sobriety evaluations, allowing the original police officer to search your vehicle and find evidence leading to your DUI-DWI arrest, is an illegal search and unconstitutional. Once stopped, your refusal to consent to a search before your arrest cannot factor into the reasonable suspicion to detain you. It is not probable cause by itself to search you and your vehicle.
Searches based on illegal goods or contraband in "plain sight"
Certainly, anything illegal or contraband that is "in plain sight" within or on your vehicle (such as an illegal attachment or faulty piece of equipment) can be cited by the police as justification for a further search and used against you in your case. Then, at the time of your arrest, the police have certain rights to search not only you, but also the passenger compartment and any containers found in the passenger compartment of your vehicle. The purpose of such a search is typically justified by claiming that such a search was needed to determine if other evidence of the criminal act is present.
"Inventory search" of your vehicle when it is impounded by police
In traffic arrests following a DUI-DWI investigation, a different kind of search takes place in almost all cases. If no "sober" driver is available to drive your vehicle away, it will likely be towed, by order of the police. A search done prior to your vehicle being towed away (called an "inventory search") is supposed to be done to assure that if valuables inside the vehicle disappear while the vehicle is impounded, the police department will not be held accountable.
Contraband can often be discovered during an "inventory search"
Because almost every custodial arrest leads to a vehicle impound and the "inventory search," you should never keep any contraband items in your vehicle. Most common are illegal drugs such as cocaine and marijuana, but sometimes the police will seize prescription painkillers or anti-anxiety medications that are not in a proper container or that are prescribed to someone else. Other types of "contraband" items might include child pornography, an unlicensed weapon, an illegal (profane) bumper sticker, or obviously stolen merchandise.
Police may be able to search your vehicle without a warrant if you leave it on the side of the road
Additionally, if you wreck your vehicle and leave it off the shoulder of the road, the police may be able to legally search the vehicle without the necessity of a warrant. The existence of the wrecked vehicle will authorize a search for victims or identification of the owner of the vehicle. A purse found inside an abandoned vehicle can be searched. However, a passenger's purse (after she was asked to step out of the vehicle) cannot legally be searched.
DUI-DWI and unlawfully seized physical evidence
In almost every DUI-DWI case, this is the sequence of events. In most cases, little chance exists that any other evidence will be "seized" by the police in order to be used against you later at your DUI-DWI trial. However, if for any reason, the DUI-DWI case against you involves physical evidence that was taken from you in unlawfully, your attorney may then be able to have this harmful evidence excluded from consideration at your trial. One of the more common successful challenges has been when police open locked or closed containers to look for illegal items.