Understanding the Four Phases of an Indiana OWI Traffic Stop
An Indiana OWI traffic stop can be understood in four practical phases: Vehicle in Motion, Officer Contact, Field Sobriety Tests, and Chemical Tests.
Each phase creates a different kind of evidence—and a different defense question. The officer first evaluates the driving, then what happens face-to-face, then roadside sobriety performance, and finally breath or blood evidence. A good OWI defense reconstructs all four instead of starting and ending with the BAC number.
The OWI case is built one phase at a time.
The strongest defense review does the same thing: driving and the stop, officer contact, field testing, and chemical testing—each compared against the video, reports, legal standards, and technical records.
An OWI stop happens quickly from the driver's perspective. From the officer's perspective, however, the investigation develops in stages. What the officer observes in one phase is often used to justify moving into the next.
That makes the four-phase framework useful for a defense. It forces the case into chronological order. What justified the stop? What did the officer actually see and hear at the window? What did the field sobriety testing really show? And was the final breath or blood evidence lawfully and reliably obtained?
This article uses the four-phase structure most useful to someone facing an Indiana OWI case: Vehicle in Motion, Officer Contact, Field Sobriety Tests, and Chemical Tests. Within those sections, current NHTSA materials and Indiana law help explain what police are looking for and what a defense lawyer should examine.
| Phase | What happens | Primary defense question |
|---|---|---|
| 1. Vehicle in Motion | Officer watches the vehicle and initiates the traffic stop. | Was there a lawful reason to stop the vehicle, and does the video support the officer's description? |
| 2. Officer Contact | Officer speaks with the driver and looks for signs of impairment. | What did the officer actually observe, and did those facts justify expanding the investigation? |
| 3. Field Sobriety Tests | Officer uses roadside testing and other observations to assess impairment and probable cause. | Were the tests fairly administered, interpreted, and affected by conditions or medical issues? |
| 4. Chemical Tests | Officer seeks roadside screening and/or evidentiary breath or blood testing. | Was the test lawfully obtained, properly administered, and supported by the required technical foundation? |
What is the officer looking for before pulling you over?
The first phase begins before the officer ever speaks to the driver. The officer is observing the vehicle in motion and deciding whether there is a lawful basis to initiate a traffic stop.
NHTSA training materials identify driving behaviors that can contribute to an impaired-driving investigation, including weaving, lane-position problems, wide turns, inconsistent speed, delayed responses, braking problems, almost striking objects, and other unusual driving. See the NHTSA SFST Participant Manual.
But an Indiana OWI stop does not have to begin with obvious impaired driving. An officer can lawfully stop a vehicle for an ordinary traffic violation—speeding, a lane violation, an equipment violation, or another valid traffic basis—and only later develop suspicion of intoxication.
The officer may also watch how the driver responds once the emergency lights activate. A delayed stop, sudden braking, hitting a curb, stopping in an unsafe place, or additional lane movement may be documented as part of the overall investigation.
For the defense, the key is to identify the exact reason police say they stopped the car and compare that claim to the objective evidence. Dash-camera footage can be especially important. A report may describe repeated weaving while the video shows a single brief movement near a faded lane marker. Road construction, weather, traffic, lane width, and roadway condition can all provide context.
The legal question is not whether the officer had a hunch that the driver might be impaired. The stop itself needs a constitutionally sufficient basis. Indiana appellate courts continue to review OWI stops under both the Fourth Amendment and Article 1, Section 11 of the Indiana Constitution.
The first question is not 'What was the BAC?' It is whether police lawfully got the opportunity to investigate at all.
The reason for the stop
Identify the traffic statute, driving behavior, dispatch report, welfare concern, or other fact the officer relied on.
What the video actually shows
Compare the report to dashcam, roadway markings, weather, traffic, timing, and the driver's response to the emergency lights.
An unlawful traffic stop can affect evidence gathered afterward. When the initial seizure lacks lawful justification, the defense may have a motion-to-suppress issue involving observations, statements, field testing, and chemical evidence that flowed from the stop. See the separate OWI suppression guide.
What is the officer evaluating when they reach the window?
Once the vehicle is stopped, the investigation moves into officer contact. This is the face-to-face phase: the officer talks with the driver, requests license and registration, watches the driver's behavior, and decides whether the encounter should remain an ordinary traffic stop or become an OWI investigation.
The familiar categories are sight, sound, and smell. The officer may document bloodshot or watery eyes, facial appearance, unusual movements, fumbling, difficulty locating documents, speech patterns, odor of an alcoholic beverage, odor of marijuana, open containers, or other physical observations.
The officer is also listening to what the driver says. Questions such as where the driver is coming from, whether they drank, how much they drank, when the last drink occurred, whether medications were taken, and whether drugs were used can generate evidence that later appears in the probable-cause affidavit.
That does not make every observation a reliable indicator of impairment. Bloodshot eyes can result from fatigue, allergies, contacts, smoke, or ordinary irritation. Nervousness is unsurprising during a police encounter. The odor of an alcoholic beverage may show consumption but does not by itself identify how much was consumed or establish impairment. A body camera can allow the defense to compare 'slurred speech' or 'confusion' to what the person actually sounded like.
The officer may also use divided-attention observations before formal field tests begin. Producing a license while answering questions, following several instructions, exiting the vehicle, walking to a testing area, or dropping an item may later be described as evidence of impairment.
This is also a major legal transition point. Even if the original traffic stop was valid, police cannot use that as unlimited authority to detain someone indefinitely. A defense lawyer should identify when the traffic matter was extended into an OWI investigation and what facts existed at that moment.
| Observation | How the State may use it | What the defense should compare |
|---|---|---|
| Eyes / appearance | Physical indicator of possible impairment | Bodycam, lighting, fatigue, allergies, contacts, normal appearance |
| Speech | Slurring, delay, confusion | Actual audio, accent, baseline speech, medical issues |
| Odor | Evidence of alcohol or another substance | Source of odor, passengers, vehicle vs. person, containers |
| Documents | Fumbling or divided-attention difficulty | Instructions, lighting, wallet location, actual performance |
| Statements | Admission to drinking, drugs, medication, timeline | Exact wording, full context, custody/Miranda issues |
| Exit / walk | Balance or coordination | Surface, footwear, injury, slope, officer instructions, video |
Stay calm and do not physically resist or argue the stop on the roadside. Provide documents that the law requires and comply with lawful safety commands. You do not improve an OWI case by volunteering a detailed story, estimating your BAC, or guessing how much alcohol remains in your system. Miranda is not automatically required for every roadside question; the custody-and-interrogation analysis is more specific.
What are field sobriety tests supposed to show?
The third phase is roadside field sobriety testing. This is where officers move from general observations to structured physical and divided-attention tasks designed to help them assess impairment and decide whether probable cause exists for an arrest.
NHTSA’s standardized field sobriety test battery consists of three tests: Horizontal Gaze Nystagmus (HGN), Walk-and-Turn, and One-Leg Stand. See NHTSA’s SFST resources.
HGN looks for specified forms of involuntary eye movement as the officer moves a stimulus in front of the driver’s eyes. It is different from the balance tests and depends heavily on training, positioning, timing, and proper administration.
Walk-and-Turn is a divided-attention exercise. The driver must listen to and remember instructions, assume a starting position, walk heel-to-toe, turn in the prescribed manner, and return. Officers are trained to look for specified clues rather than simply deciding whether the person 'looked drunk.'
One-Leg Stand likewise requires the driver to follow instructions, raise one foot, maintain the position, count as directed, and avoid particular balance-related clues.
Indiana officers may also use additional roadside exercises. The Romberg balance test, for example, can be used to evaluate balance and internal time estimation, particularly in some drug-related investigations. But it is important to describe it accurately: Romberg is not one of NHTSA’s three standardized field sobriety tests.
Field-testing conditions matter. Uneven pavement, gravel, slope, rain, snow, wind, poor lighting, passing traffic, unsuitable footwear, age, prior injury, neuropathy, inner-ear problems, neurological conditions, anxiety, language barriers, or difficulty understanding instructions can affect performance.
The officer’s administration matters too. Were the instructions complete? Was the test properly demonstrated? Did the officer rush the driver? Did the report claim a clue the video does not show? Did the officer know about a physical limitation? Was HGN performed at appropriate distances and timing?
A testing problem does not automatically mean the entire test is constitutionally 'suppressed.' Sometimes the issue is whether the driver was lawfully detained long enough to perform the test. Sometimes it is whether the State can lay the necessary foundation. And sometimes the problem simply makes the officer's interpretation less persuasive.
HGN. Eye-movement testing; administration and training matter.
Walk-and-Turn. A standardized divided-attention walking test.
One-Leg Stand. A standardized divided-attention balance test.
| Question | Why it matters |
|---|---|
| Were the instructions clear and complete? | Performance cannot be fairly evaluated without knowing what the driver was told to do. |
| Did the officer demonstrate the test properly? | The demonstration is part of the driver's opportunity to understand an unfamiliar task. |
| Was the surface reasonably suitable? | Slope, gravel, ice, traffic, darkness, or obstacles can affect balance and performance. |
| Were medical or physical limitations identified? | Orthopedic, neurological, vision, balance, and other conditions can affect particular tests. |
| Does the video match the report? | Bodycam often permits direct comparison between claimed clues and actual performance. |
| Were nonstandard tests described as standardized? | Romberg and other exercises should not be confused with NHTSA's three-test standardized battery. |
The report says 'failed.' The video may show something much more complicated.
A defense review should examine each instruction, each claimed clue, the testing conditions, the driver's physical limitations, and whether the roadside evidence actually supported probable cause.
What happens when the OWI investigation moves to breath or blood?
The fourth phase is chemical testing. At this point, the investigation moves from observations and roadside performance to an attempt to measure alcohol concentration or identify drugs or controlled substances through breath or blood evidence.
There are several different kinds of chemical-test evidence, and they should not be lumped together.
A portable breath test (PBT) is generally a roadside screening tool used during the investigation and probable-cause decision. It is not the same instrument or process as Indiana’s certified evidentiary breath test. The safer legal description is that its use and admissibility depend on the purpose, foundation, and circumstances—not the categorical claim that a PBT can never appear in court.
An evidentiary breath test is administered through Indiana’s regulated breath-testing program. The Indiana State Department of Toxicology says breath-test operators must be recertified every two years and evidentiary instruments are inspected, serviced, and certified at least every 180 days.
The defense can examine operator certification, instrument certification, the approved method, the test ticket, test timing, the deprivation period, sample sequence, error messages, and the underlying documentation. ISDT publishes its policies and approved-method materials and maintains an operator/instrument certification database.
Blood testing raises a different set of questions. Was the sample obtained by consent, warrant, or another lawful basis? Who drew the blood? What protocol applied? How was it labeled, stored, transported, and tested? If the sample was drawn at a hospital for medical treatment, how police obtained the sample or records may create additional legal issues.
Indiana’s implied-consent law also creates driving-privilege consequences. The Indiana BMV currently explains that a failed chemical test can produce a suspension of up to 180 days and a refusal can produce a suspension of up to two years, depending on the circumstances.
A refusal is therefore not simply 'no BAC evidence.' It can create its own license issue, and police may in some cases seek a search warrant for blood after a refusal. The criminal case, refusal suspension, and any later request for specialized driving privileges need to be evaluated separately.
The defense should also distinguish legality from reliability. A blood draw may be supported by a valid warrant but still present chain-of-custody or laboratory issues. A certified breath test may have been lawfully requested but still depend on whether the State can establish the required technical foundation.
| Test / procedure | Role in the OWI investigation | Defense issues |
|---|---|---|
| Portable Breath Test | Roadside screening / probable-cause information | Device use, timing, purpose, foundation, how State seeks to use result |
| Certified Breath Test | Evidentiary alcohol-concentration test | Operator/instrument certification, approved method, deprivation period, test record |
| Blood Test | Alcohol and/or drug toxicology | Warrant/consent, collector, protocol, chain, storage, laboratory analysis |
| Refusal | Implied-consent event with license consequences | Advisement, request, response, warrant issues, BMV suspension |
The chemical number is not self-proving. Breath and blood evidence have legal and technical foundations. The defense should review how the sample was obtained, who handled it, what procedure applied, whether the State's records support admissibility, and what the result actually proves.
How does a defense lawyer review the entire OWI stop?
The four phases should be placed on one timeline. Start with what police observed before the emergency lights. Add the exact time of the stop, the first contact at the window, every material statement, when the driver exited, field-test instructions and performance, any PBT, the arrest decision, implied-consent advisement, evidentiary breath or blood collection, and booking.
Then ask whether the evidence from each phase justified the next one. A valid speeding stop does not automatically prove the later OWI detention was justified. Poor field sobriety performance cannot retroactively create a lawful reason for a stop that was unconstitutional from the beginning. And a high chemical-test result does not automatically cure a defective test procedure or unlawful blood seizure.
Finally, separate the kind of challenge involved. The stop may create a constitutional suppression issue. Officer-contact observations may be contradicted by video. Field sobriety testing may raise administration, medical, reliability, or probable-cause questions. Breath and blood testing can raise warrant, implied-consent, foundation, certification, chain-of-custody, and scientific issues.
| Phase | Most important records | What counsel is testing |
|---|---|---|
| 1. Vehicle in Motion | Dashcam, dispatch, traffic citation, officer report | Reason for stop and accuracy of driving allegations |
| 2. Officer Contact | Bodycam, audio, statements, timestamps | Accuracy of impairment observations and basis to expand detention |
| 3. Field Sobriety Tests | Bodycam, SFST forms, PBT, medical history | Administration, conditions, performance, probable cause |
| 4. Chemical Tests | Implied-consent forms, certifications, test ticket, warrant, blood/lab file | Lawful acquisition, technical foundation, reliability |
Review the case in the order it actually happened.
If you were arrested for OWI, I can review all four phases—the driving, officer contact, field sobriety tests, and chemical testing—to identify suppression issues, evidentiary problems, testing weaknesses, and the evidence the State can actually use.
Frequently asked questions
01What are the four phases of an Indiana OWI traffic stop?
For this practical defense framework, the four phases are Vehicle in Motion, Officer Contact, Field Sobriety Tests, and Chemical Tests.
02Does an officer need to see obvious drunk driving before making an OWI stop?
No. A valid traffic violation or another lawful basis can justify the initial stop even if the officer does not yet have reasonable suspicion of intoxication. The OWI investigation may develop during Officer Contact.
03What does an officer look for during Officer Contact?
Officers may document odor, eyes, speech, coordination, document handling, statements, divided-attention behavior, containers, and how the person exits or walks. Those observations should be compared to body-camera evidence and alternative explanations.
04What are the three standardized field sobriety tests?
NHTSA's standardized battery is Horizontal Gaze Nystagmus, Walk-and-Turn, and One-Leg Stand. Officers may use other exercises, including Romberg, but those are not part of NHTSA's three standardized tests.
05Can bad field sobriety testing get an OWI dismissed?
A testing problem can weaken probable cause or trial evidence, but the remedy depends on the problem. Poor administration may affect reliability or weight; an unlawful detention may support suppression; and the State may still have other evidence.
06Is a portable breath test the same as a certified breath test?
No. A roadside PBT is principally a screening/probable-cause tool. Indiana's certified evidentiary breath test is part of the regulated chemical-testing process and has separate certification and approved-method requirements.
07What happens if I refuse an Indiana chemical test?
A refusal can create significant driver's-license consequences under Indiana's implied-consent law and police may sometimes seek a warrant for blood. The criminal and license issues should be evaluated separately.
08What should I write down after an OWI arrest?
Record the reason given for the stop, driving conditions, officer questions and observations, statements you made, field-test instructions and conditions, any medical limitations, implied-consent advisement, breath or blood procedures, and approximate timing while your memory is fresh.
This article is general information about Indiana OWI investigations, not legal advice, and reading it does not create an attorney–client relationship. The four-phase structure used here is the practical framework described in the article: Vehicle in Motion, Officer Contact, Field Sobriety Tests, and Chemical Tests. NHTSA terminology, constitutional law, Indiana statutes, implied-consent procedures, testing standards, and local practices can differ or change, and every case turns on its facts. Reviewed August 2026. Attorney advertising.
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