How a Colorado DUI Defense Attorney Can Investigate the Evidence After an Arrest
A DUI arrest is not the end of the fact-finding process. It is the beginning of a case that may turn on video, reports, testing records, timing, witness accounts, and the legal basis for the stop and arrest. A criminal defense attorney’s job is not to assume that an arrest proves guilt. It is to obtain the available evidence, evaluate it carefully, and advise the client about what it may mean.
This article provides general information about Colorado DUI investigations. It is not legal advice for any case, and no investigation guarantees a dismissal or other outcome.
Start by Preserving What Can Disappear
Some important evidence can be overwritten or become harder to locate with time. Early in a case, defense counsel may take steps to identify and preserve material such as:
police body-camera and dash-camera footage;
jail, booking, or breath-test-room video;
911 recordings, dispatch audio, and computer-aided dispatch logs;
surveillance footage from nearby businesses, homes, or parking lots;
vehicle-tow and impound records;
photos, videos, rideshare receipts, phone-location data, and other client records; and
names and contact information for potential witnesses.
The purpose is simple: create the most complete and accurate timeline possible before memories fade or recordings are routinely deleted.
Review the Reason for the Stop and the Basis for the Arrest
A defense investigation generally begins with the sequence of events. Why did the officer contact the driver? What observations were reported before the stop? What happened during the encounter? When was the person detained or arrested? Did the officer have jurisdiction to conduct the stop?
Counsel may compare the officer’s written report with video, dispatch information, witness accounts, and physical evidence. This comparison can identify points that need further analysis, including whether the evidence consistently supports the stated reason for the stop and the probable-cause determination. The inquiry is fact-specific; an inconsistency does not automatically determine the result, but it should be investigated.
Examine Roadside Exercises and Preliminary Testing in Context
Police reports often describe roadside exercises, observations about speech or balance, and a preliminary breath screening. A lawyer can evaluate the actual conditions rather than relying solely on a conclusion in a report.
Relevant questions may include:
Were the exercises recorded, and does the video match the report?
What were the weather, road, lighting, footwear, traffic, or medical conditions?
Were instructions clear and consistently given?
Did an injury, disability, age, fatigue, anxiety, or other condition affect performance?
What was the purpose of a preliminary screening test, and how was it used?
Under Colorado law, a preliminary screening breath test may be used by an officer in determining probable cause, but it does not substitute for the post-arrest chemical testing required under the expressed-consent statute. C.R.S. § 42-4-1301; C.R.S. § 42-4-1301.1
Investigate the Chemical-Test Process
Chemical evidence can be important, but it should be evaluated as evidence—not treated as a conclusion that needs no review. Colorado’s expressed-consent statute contains specific rules addressing requests for breath or blood testing for alcohol and, when appropriate, blood, saliva, or urine testing for drugs. The statute also includes timing and cooperation requirements. C.R.S. § 42-4-1301.1
A defense attorney may seek and evaluate records concerning:
the date and time of driving, contact, arrest, and sample collection;
the officer’s advisement and the type of test requested or selected;
the test result and underlying data or laboratory documentation;
instrument records, certification materials, maintenance information, and operator records when applicable;
the collection, labeling, transport, and handling of a blood or other sample;
medical circumstances or extraordinary events that may have affected testing; and
the factual basis for an alleged refusal.
Colorado law permits a DUI-per-se defendant to offer direct and circumstantial evidence that may show a disparity between a test result and other facts, including evidence bearing on whether the analysis was defective or inaccurate. The law likewise makes the proper operation of testing devices relevant at trial. C.R.S. § 42-4-1301
Evaluate the Full Picture, Not One Number or One Observation
Colorado law provides certain permissible inferences based on alcohol or drug-test results, but it does not make every DUI case a one-item case. The law also allows other competent evidence to be considered on the question of influence or impairment. C.R.S. § 42-4-1301
That means a thorough investigation may include information that places the State’s evidence in context, such as:
witnesses who observed the person before or after driving;
receipts and objectively verifiable timing information;
medical records or medication information where appropriate;
evidence concerning driving behavior or the lack of an unsafe-driving event;
the person’s appearance, speech, coordination, and statements on video; and
circumstances affecting the reliability or interpretation of a test.
For drug-related allegations, the investigation may be especially fact-specific. The attorney should carefully distinguish between evidence of a substance and evidence bearing on whether that substance impaired driving at the legally relevant time.
Compare Reports, Recordings, and Documents for Accuracy
DUI cases can generate multiple accounts: an incident report, arrest affidavit, summons, booking record, chemical-test documents, dispatch log, and video recordings. Counsel can build a timeline and compare each source for omissions, differences, and facts that require explanation.
For example, an officer’s report may describe a particular driving pattern, statement, or performance on a roadside exercise. Video, dispatch data, or a neutral witness may provide helpful context. Conversely, the evidence may corroborate the report. A defense lawyer’s role is to identify what the evidence shows and explain its likely significance to the client.
Investigate Refusal Allegations and Administrative Evidence
An alleged refusal can affect both the criminal case and the driver’s-license process. The relevant questions may include what was requested, what advice or advisement was given, whether the person was capable of completing the requested test, whether any medical issue was involved, and what was recorded.
The investigation should address the criminal and licensing tracks separately. A criminal court outcome and an administrative license outcome are not necessarily the same, and the documents, deadlines, and standards may differ.
Use the Investigation to Make Informed Decisions
The goal of a defense investigation is not to manufacture a defense or promise a result. It is to give the client a reliable foundation for important decisions: whether to challenge evidence, request additional records, prepare for a hearing, negotiate a resolution, or proceed toward trial.
A prompt review is valuable because it helps preserve evidence and identify deadlines. After a DUI arrest, a person should keep all paperwork, avoid public discussion of the incident, follow bond and driving restrictions, and consult a Colorado defense attorney who can evaluate the evidence.
This article is for general educational purposes only and does not create an attorney-client relationship.