DUI arrests require precise procedures to withstand legal scrutiny. A single misstep can result in case dismissal, regardless of actual impairment.
We at Fraiberg & Pernie have seen countless cases where procedural errors undermined otherwise solid arrests. This DUI checklist for law enforcement provides the framework officers need to build bulletproof cases while protecting constitutional rights.
What Makes a DUI Traffic Stop Legally Valid?
Fourth Amendment Foundation for Traffic Stops
Officers need reasonable suspicion to initiate any traffic stop under the Fourth Amendment. This standard requires more than a hunch-specific, articulable facts must justify the detention. Michigan courts consistently throw out cases where officers cannot demonstrate this threshold.
Equipment violations like cracked windshields or broken taillights provide clear grounds. Traffic violations such as speeding, weaving, or running red lights meet this standard. Driving behaviors that suggest impairment-swerving between lanes, inconsistent speeds, or nighttime operation without headlights-also justify stops.
Officers must document these observations immediately, as memory fades and defense attorneys will scrutinize every detail during cross-examination.
Documentation Standards That Hold Up in Court
The quality of documentation determines case strength. Vague descriptions like “erratic operation” won’t survive cross-examination. Officers should record specific observations: “Vehicle crossed the center line three times in 0.2 miles” or “Speed varied between 35 and 55 mph in a 45 mph zone over 30 seconds.”
Dashboard cameras provide objective evidence that supports written reports. The National Highway Traffic Safety Administration research shows that certain patterns correlate strongly with impairment: weaving within the lane indicates a 65% probability of intoxication, while straddling the center line suggests 65% probability.
Time stamps, weather conditions, and traffic density add context that strengthens reports. Poor documentation gives defense attorneys ammunition to challenge the entire stop’s validity.
Constitutional Protections Officers Must Respect
Once stopped, drivers retain constitutional rights that officers must respect. The stop’s scope must match its original justification-a broken taillight stop cannot immediately become a full DUI investigation without additional probable cause.
Officers need specific indicators of impairment to extend the detention: bloodshot eyes, alcohol odor, slurred speech, or fumbling with documents. Michigan’s implied consent law requires proper advisement at arrest (not during initial questioning). Miranda warnings become necessary only when custodial interrogation begins.
Officers who rush these procedures create appealable issues that skilled attorneys exploit effectively. The transition from traffic stop to DUI investigation requires careful attention to proper field sobriety test administration and standardized procedures.
How Do Officers Administer Field Sobriety Tests Correctly?
The Three Tests That Matter Most
The National Highway Traffic Safety Administration recognizes only three standardized field sobriety tests that hold up in court. The horizontal gaze nystagmus test checks for involuntary eye movement when a suspect follows an object. Officers must position the stimulus 12-15 inches from the suspect’s nose and move it at a specific speed. The walk-and-turn requires nine heel-to-toe steps in a straight line, then a turn and return. The one-leg stand demands that suspects hold one foot six inches off the ground for 30 seconds while they count aloud.
These tests show 91% accuracy when officers administer them correctly together. Individual test reliability drops significantly when officers deviate from protocols. Any modification to standardized procedures compromises the scientific validity that courts require.
Training Requirements That Prosecutors Demand
Officers must complete 40-hour certification programs as of 2023 plus annual recertification to testify about test results. Many departments skip refresher courses or allow uncertified officers to conduct tests. Michigan courts require officers to demonstrate current certification and proper administration techniques during testimony.
Officers who guess at procedures or modify tests create reasonable doubt that defense attorneys exploit. Weather conditions, uneven surfaces, and medical conditions invalidate results, but officers often ignore these factors during roadside testing. Courts reject testimony from officers who cannot prove they followed standardized protocols exactly.
Documentation Standards That Survive Cross-Examination
Proper test documentation requires specific observations in measurable terms rather than subjective impressions. Officers who write “failed all tests” provide no useful evidence for prosecutors. Detailed notes must record each clue observed: “stepped off line twice during instruction phase” or “raised arms more than six inches for balance.”
Video evidence often contradicts officer reports when documentation lacks precision. Officers must note lighting conditions (streetlights, headlights, darkness), surface type (asphalt, concrete, gravel), and any factors that could affect performance. Defense attorneys scrutinize every detail, and incomplete documentation transforms solid cases into dismissed charges.
Medical Conditions That Invalidate Test Results
Officers must ask suspects about medical conditions before administering field sobriety tests. Inner ear problems, leg injuries, and neurological conditions can mimic impairment signs. Age over 65, weight over 50 pounds overweight, and certain medications also affect test performance.
Officers who ignore these factors face aggressive cross-examination about test validity. Courts exclude test results when officers fail to account for legitimate medical explanations. Proper chemical testing protocols become even more important when field sobriety tests prove unreliable due to medical factors.
What Chemical Testing Procedures Must Officers Follow?
Calibration Requirements That Courts Demand
Chemical tests provide the most critical evidence in DUI cases, yet officers routinely compromise results through procedural failures. Michigan requires breathalyzer calibration every 120 days with certified reference standards, but many departments skip this requirement. The Datamaster DMT machines used statewide must undergo daily accuracy checks and monthly linearity tests.
Officers who cannot produce calibration records watch prosecutors drop cases immediately. Departments that fail to maintain proper calibration logs or use expired reference solutions face automatic dismissals. Courts reject chemical evidence when officers cannot prove machines operated within acceptable parameters.
Breath Test Administration Standards
Officers must observe suspects for 15 minutes before breath tests to prevent mouth alcohol contamination. Burping, vomiting, or consuming anything during this period invalidates results. The observation period must be continuous and documented precisely (officers who check phones or handle other duties create reasonable doubt).
Two breath samples taken within 0.02 BAC of each other are required, with tests administered 2-15 minutes apart. Radio frequency interference from police radios can skew results by 0.01 BAC or more. Officers must turn off all electronic devices within three feet of the machine during tests.
Blood and Urine Collection Protocols
Blood tests require certified phlebotomists and proper chain of custody documentation. Officers cannot draw blood themselves or allow unqualified personnel to perform collections. Each vial must be labeled immediately with suspect information, collection time, and officer identification.
Urine tests demand split samples and specific collection procedures that most officers ignore. The suspect must provide two separate samples (with the first discarded after 20 minutes). Officers must witness the collection process while respecting privacy rights and maintaining proper chain of custody throughout.
Implied Consent Warnings That Hold Up
Michigan’s implied consent law requires specific language read at arrest time, not during initial questioning. Officers who paraphrase warnings or read them too early create appealable issues. The warning must explain license suspension consequences clearly: one year for first refusal, two years for second refusal within seven years.
Officers must also advise that refusing the test creates a separate civil infraction with additional penalties. Many officers rush through this advisement or fail to give suspects adequate time to make informed decisions. Courts exclude chemical test results when officers violate implied consent procedures, regardless of actual BAC levels.
Final Thoughts
Proper DUI procedures directly determine case outcomes in Michigan courts. We at Fraiberg & Pernie have witnessed strong cases collapse due to procedural errors that defense attorneys exploit ruthlessly. Officers who follow this DUI checklist for law enforcement create solid cases that withstand aggressive cross-examination.
Training failures cost departments thousands of dismissed cases annually. Officers need continuous education on constitutional requirements, field sobriety test protocols, and chemical testing procedures. Departments that prioritize accountability and certification see conviction rates increase significantly while they reduce successful appeals.
Constitutional protections remain paramount during DUI enforcement. Officers who rush procedures or skip required steps create appealable issues that skilled attorneys identify immediately. When procedural errors occur, experienced DUI attorneys can identify these mistakes and fight for reduced charges or case dismissals across Oakland County, Wayne County, and Macomb County courts.
