In my jurisdiction, the failure to give Miranda warnings can be grounds to have the suspects statements surpressed as evidence. Generally, any statements given voluntarily to the officer prior to arrest our admissible as evidence. Once a suspect is arrested, he must be read his Miranda warnings. A failure to do so can lead to the supression of any statements made after arrest. The officer can not delay his decision to arrest in the hopes of elicitng more incriminating statements from the suspect. A person can perform well on the Field Sobriety Tests and still be arrested for DUI. If a person takes a PBT (preliminary breath test) often administed by the officer after the Field Sobriety Tests and the results is .08 or above this is generally sufficient probable cause to arrest the suspect.
Prior to taking a breath or blood sample from the suspect, the suspect must be given his implied consent warnings. A failure to properly advise a suspect of his implied consent warnings prior to a breath or blood test being administered can lead to the suppression of the results of this test..
If the case were dropped, there could still be a probation violation. If for instance, the terms of his probation required him to refrain from alcohol and there was evidence of alcohol usage such as the officers testimony that the suspect had an odor of intoxicants on his breath or the results of the PBT. In probation hearings the standard of proof to find a violation has occurred is not "beyond a reasonable doubt" as in a criminal trial but generally " beyond a preponderance of the evidence" which is a much easier standard of proof to be met.
The key words are "subsequently arrested." Under the United States Supreme Court decision in Miranda v. Arizona, the police only have to read your rights if you are arrested -- or subject to restraint that is equivalant to being arrested.
Subsequent Supreme Court decisions say that a traffic stop and DUI investigation are "minimally intrusive" and are not the equivalent of arrest. It appears the Supreme Court is made up of nine people who have never been subjected to the indignity of being ordered out of a car and asked to dance the roadside ballet in front of everybody driving past.
That means the cops generally don't have to read your rights until they slap on the cuffs.. and by then, they already have all of the statements you want.
Miranda is limited to suppression of any statements made after the point when the cops should have read the suspect his rights, not to physical evidence.
Please understand that this is a general discussion of legal principles by a California lawyer and does not create an attorney/client relationship. It's impossible to give detailed, accurate advice based on a few sentences on a website (and you shouldn't provide too much specific information about your legal matter on a public forum like Avvo, anyway). You should always seek advice from an attorney licensed in your jurisdiction who can give you an informed opinion after reviewing all of the relevant information.
This is an evolving area of the law. While I practice in California this answer is based on US Supreme Court law, which may be interpreted by IN courts differently. The Supreme Court case of Berkemer v. McCarthy interprets the 5th amendment to allow police to ask one or two questions in the investigation (pre-arrest) of a suspect for a traffic stop.
If your friend did not feel that he was free to leave and if, as usual, the officer's asked in excess of 15-20 questions then most likely your friend would be entitled to suppress his statements.
When the Miranda Warning Is Required
It doesn't matter whether an interrogation occurs in a jail, at the scene of a crime, on a busy downtown street, or the middle of an open field: If a person is in custody (deprived of his or her freedom of action in any significant way), the police must give a Miranda warning if they want to question the suspect and use the suspect's answers as evidence at trial.
If a person is not in police custody, however, no Miranda warning is required and anything the person says can be used at trial if the person is later charged with a crime. This exception most often comes up when the police stop someone on the street to question him or her about a recent crime or the person blurts out a confession before the police have an opportunity to deliver the warning.
The Miranda line of cases protects an arrestee from "custodial interrogation."
There are many different cases which develop whether someone is "in custody" and whether the Officer's statement is of the type that would elicit an incriminating response from a suspect, AKA "interrogation.”
While this can be a complicated area of law, generally, at the point after the Preliminary Alcohol Screening [which is given after the Standardized Field Sobriety Tests (SFSTs) due to the mandatory 15 minute observation period required under California's Title XVII Regulations], a suspect is arrested if the officer has probable cause to suspect a DUI based in part upon a high enough breath test result. An example would be “blowing” a .10 % BAC combined with a driving pattern, physical symptoms as well as “failing” the SFSTs.
That is when the handcuffs come out, and the suspect often gets transported in the patrol car to jail. Typically, a Miranda advisement is given in California at the booking stage at the Police or Highway Patrol station. But, generally, the suspect has already given highly incriminating answers to questions which precede the Standardized Field Sobriety Tests.
These questions include things like:
"Where are you coming from?"
"Have you consumed any alcohol?"
"How many drinks?"
"When did you start drinking?"
"When did you stop drinking?"
"When did you last eat?"
"When did you last sleep and how many hours?"
"Do you suffer from a physical medical condition?" (Important to rule out for "failing" the SFSTs)
"Are you taking medication?"
The answers to these questions can impact your chances at trial tremendously, and are almost always outside the Miranda protections. Suspects very often try to minimize the number of drinks and put the drinking farther back in time than was really the case, e.g. "I had two beers and stopped over an hour ago."
The answers to these questions also can become the basis to impeach a defendant at trial, and most suspects, wanting to cooperate, generally say things which tend to be harmful at trial.
Unfortunately, this kind of situation happens all too frequently in California.
I suggest contacting a DUI Specialist in California if you have more questions about the Pre-SFST questions and the Miranda protections.