Quick note on the case name. In the reported jurisprudence on R.A. 10586, there is no widely cited Supreme Court ruling titled People v. Navarro that has become the leading authority on the Anti-Drunk and Drugged Driving Act. In practice, however, litigators often shorthand trial or Court of Appeals dispositions by party name (e.g., an RTC/CA People v. Navarro) to refer to recurring doctrines under R.A. 10586—especially about stops at checkpoints, field sobriety testing, breathalyzer use, and proof of impairment. What follows is a comprehensive, doctrine-first article you can rely on when briefing or trying any “Navarro-type” prosecution or defense under Philippine law.

I. Statutory Framework

R.A. 10586 (2013)—the Anti-Drunk and Drugged Driving Act—criminalizes operating a motor vehicle while under the influence of alcohol and/or dangerous drugs. Core features:

Two ways to prove the offense
- Per se alcohol limits: A driver is deemed under the influence when blood alcohol concentration (BAC) meets or exceeds statutory/IRR thresholds:
  - Non-professional drivers: commonly 0.05% BAC (50 mg/dL) or higher.
  - Professional, PUV/school service/heavy equipment drivers, and drivers below 18: a much lower threshold (effectively zero tolerance under the IRR).
- Impairment (regardless of BAC): Observable signs of intoxication or drug influence proven through field sobriety tests, behavioral manifestations, witness testimony, and/or chemical tests.
Drugged driving: Operation of a vehicle under the influence of dangerous drugs (as defined by the Dangerous Drugs Act) is punishable even without an alcohol component.
Penalties scale with harm
- No injury/damage: Fine and short imprisonment; license suspension for the first offense.
- With physical injuries or property damage: Heavier penalties; longer suspension/revocation.
- If death results: Long-term imprisonment and perpetual license revocation. (Always check the latest text/IRR for exact amounts/durations when pleading or negotiating.)
Administrative overlay
- License confiscation/suspension at the point of apprehension (subject to due process).
- Vehicle impound in qualified circumstances.
- Mandatory education/rehabilitation components may be imposed as conditions for reinstatement.

II. Enforcement: From Roadside Stop to Chemical Testing

A. Lawful Stops

Traffic stops arise from (i) specific violations (swerving, overspeeding, collision), (ii) articulable suspicion of impairment (e.g., odor of alcohol, slurred speech), or (iii) lawful checkpoints.
Checkpoints must be properly set up (visible signage, marked vehicles, uniformed officers, supervisory authorization) and minimally intrusive. A “Navarro-type” challenge usually attacks:
- Absence of proper authorization or signage,
- Selective, non-neutral stopping,
- Overly intrusive questioning/searches without probable cause.

B. Field Sobriety Tests (FSTs)

Typical FSTs under the IRR:
- Horizontal Gaze Nystagmus (HGN),
- Walk-and-Turn, and
- One-Leg Stand.
Competence & training: Officers administering FSTs must be trained and certified. Common defense: Move to exclude FST results where the officer lacks certifications, fails to explain instructions, or deviates from standardized scoring.

C. Breath Testing & Chemical Analysis

Breath analyzers must be calibrated and approved; calibration logs and the operator’s training certificates are routinely demanded in evidence.
Blood/urine collection requires qualified medical personnel using DOH-accredited protocols; custody seals and chain-of-custody must be documented from draw to laboratory to courtroom.
Documentation that matters:
- Device calibration and maintenance records,
- Officer certifications (FST and breathalyzer operation),
- Consent forms or implied-consent advisories,
- Chain-of-custody log (time stamps, handlers, seals),
- Laboratory accreditation and analyst credentials,
- Dash/body-cam footage and incident reports.

III. Constitutional Guardrails

Seizures & warrantless arrests A DUI arrest is often justified under the in flagrante delicto rule (committed in the officer’s presence) or as a moving vehicle stop escalating to probable cause. The reasonableness of the stop and specific, articulable facts supporting impairment are pivotal.
Searches
- Breath tests are generally treated as minimally intrusive administrative measures tied to licensing and roadway safety.
- Blood draw is more invasive and typically requires valid consent under the implied-consent regime or clear exigency with medical necessity. Courts scrutinize voluntariness and the absence of coercion.
Implied Consent (Sec. 15; IRR) Licensed drivers are deemed to have consented to alcohol/drug testing when lawfully apprehended.
- Refusal triggers license confiscation/suspension and can carry adverse inferences in administrative proceedings.
- For criminal conviction, prosecutors still prudently build independent proof of impairment (FST, driving behavior, demeanor) to avoid relying solely on refusal.
Due Process & Chain of Custody Lapses in chain-of-custody or laboratory accreditation can be fatal to the State’s case—especially in drugged-driving prosecutions where proof hinges on toxicology.

IV. Elements and Burdens at Trial

What the Prosecution must typically establish:

Operation of a motor vehicle (not merely sitting in a parked car unless the facts show control/operation).
Influence of alcohol/drugs at the time of operation, proven by:
- Valid BAC reading at or above the applicable threshold, or
- Impairment evidence (driving pattern, demeanor, FST performance, witness accounts, officer observations), and
- Foundational authenticity: certifications, calibration logs, chain of custody, and proper administration.

Defense pressure points:

Unlawful stop/checkpoint → move to suppress all downstream evidence.
Invalid or non-standardized FSTs → challenge reliability and weight.
Breathalyzer issues → calibration gaps, uncertified operators, improper 15-minute observation period, failure to check for mouth alcohol/foreign substances.
Blood/urine defects → absence of consent, improper draw, broken chain, non-compliant lab.
Causation & timing → delays between driving and testing; post-incident drinking claims (the “hip-flask” defense).
Impairment alternatives → fatigue, medical conditions, medications that mimic intoxication cues.

V. Sentencing & Collateral Consequences

License consequences: Graduated suspensions (first and subsequent offenses) leading up to perpetual revocation where death results or for repeat professional/PUV offenders.
Vehicle impound/installment of interlocks: While not universally mandated, courts may look favorably on ignition interlock or treatment/education as rehabilitative measures in plea discussions.
Insurance & civil liability: Conviction or solid proof of intoxication impacts insurance coverage, contributory negligence, and damages in related civil actions.

VI. Litigation Playbooks

A. Prosecution Checklist

Validate the stop (checkpoint memo, video, reports).
Lock down FST: officer certifications, clear instructions given, standardized scoring sheets, video if available.
For breath tests: machine approval documents, calibration logs, operator’s cert, observation period record, test printouts with timestamps.
For blood/urine: consent; medical personnel credentials; collection kit records; lab accreditation; analyst testimony; chain of custody (every handoff).
Anticipate motions to suppress and Daubert-style reliability challenges; prepare judicial affidavits of tech witnesses.

B. Defense Toolkit

Motion to Suppress: unlawful stop/checkpoint, lack of probable cause, custodial admissions without counsel, coerced “consent.”
Evidentiary objections: authentication, hearsay within laboratory reports, best evidence of calibration (not just an officer’s say-so).
Expert testimony: on FST error rates, breath testing physiology (mouth alcohol, GERD, partition ratios, temperature), retrograde extrapolation weaknesses, and drug impairment symptomatology.
Reasonable doubt themes: “bad driving ≠ intoxication,” “machine said so ≠ proof beyond reasonable doubt,” “broken chain, broken case.”

VII. Compliance & Policy for Transport Operators and Fleets

Internal alcohol/drug policies: Zero-tolerance aligned with IRR; random testing compliant with DOLE/DOH protocols.
Training: Supervisors and drivers on impairment cues and incident response (post-crash isolation, no alcohol post-incident).
Documentation: Maintain training logs, device calibration records (if using screening tools), and incident kits (incident report forms, witness statement templates).

VIII. Practical Templates (for Counsel)

Motion to Suppress (Checkpoint/Stop)—alleging lack of authorization, signage, neutral criteria, and articulable suspicion.
Motion in Limine (FST Evidence)—requiring strict foundational proof of training, standardized instructions, and scoring.
Subpoena Duces Tecum—for calibration logs, operator/analyst certifications, lab accreditation, collection kit lot numbers, surveillance or body-cam footage.
Proposed Jury (Court) Questions—on timing of tests, observation periods, mouth alcohol protocols, and chain-of-custody breaks.

IX. “Navarro-Type” Lessons Summarized

Stops must be clean: If the stop or checkpoint fails the reasonableness test, everything after it is at risk.
FSTs are only as good as their administration: No standardized instructions or scoring → weight plummets.
Machines don’t convict by themselves: Calibration + operator certification + observation protocol + printouts are the quartet.
Blood/urine cases rise and fall on chain-of-custody: Treat it like a Dangerous Drugs Act prosecution in terms of rigor.
Refusal matters, but isn’t everything: It has administrative bite and evidentiary relevance, but prosecutors should still prove impairment.

X. Takeaways

R.A. 10586 prosecutions are forensically driven and procedure-sensitive.
Defense success often lies in process auditing—from checkpoint memos to lab seals.
Prosecutors must paper the file with foundational documents and prepare technical witnesses.
For transport operators, prevention and documentation are the best risk controls.

Final Checklist (Pin-worthy)

Lawful stop/checkpoint papers
Trained officer + standardized FST forms
Breathalyzer approval + current calibration logs + operator cert + observation period log
Blood/urine consent + qualified medical draw + sealed kit + lab accreditation + complete chain
Dash/body-cam, incident reports, and witness statements
Penalty exposure memo (criminal + administrative + civil)

If your “People v. Navarro” refers to a specific RTC/CA disposition you’re handling, slot its facts into the framework above: test the stop, dissect the FST, audit the device/lab, and tighten or attack the chain. That is where these cases are won.