Challenging Blood or Urine Evidence in a New Jersey DWI Case

Blood and urine evidence can become central in a New Jersey DWI prosecution, particularly after a serious accident or when police suspect drug impairment.

But a laboratory result is not automatically admissible simply because it appears in discovery.

The State may have to establish that the sample was lawfully obtained, collected in a medically acceptable manner, properly identified and preserved, reliably tested, and introduced through competent witnesses. The defense should also examine whether the chemical result actually proves impairment at the time of driving.

For a broader overview of New Jersey DWI law and defenses, visit our New Jersey DWI Lawyer Homepage.

When Can Police Obtain a Blood Sample?

A compelled blood draw constitutes a search under the Fourth Amendment.

Police generally need valid consent, a search warrant supported by probable cause, or a recognized exception to the warrant requirement.

The natural dissipation of alcohol or drugs from the bloodstream does not automatically create an emergency allowing police to bypass a warrant.

In State v. Adkins, 221 N.J. 300  (2015), applying Missouri v. McNeely, 569 U.S. 141 (2013), the New Jersey Supreme Court held that exigency must be evaluated under the totality of the circumstances. Dissipation is important, but it does not create a categorical warrant exception.

The defense should therefore reconstruct the warrant timeline:

When did probable cause develop? How long would obtaining a warrant have taken? What other duties were officers handling? Was there a genuine reason judicial authorization could not reasonably be obtained?

The Warrant Application and Recording Matter

Where police obtain a blood-draw warrant, the defense should review more than the signed warrant.

The actual application establishes what the officer told the judge to obtain authorization.

That can include observations of driving, field sobriety performance, witness statements, admissions, evidence of drug or alcohol use, accident circumstances, and the reason police sought blood rather than relying on another test.

If sworn oral testimony is used to support a telephonic warrant, there should be a reliable contemporaneous record of what was presented to the judge. New Jersey appellate decisions have treated failures to preserve the record underlying telephonic warrants as potentially serious because later review depends on knowing what information the issuing judge actually received.

That recording should be compared with the officer’s reports and body-camera footage.

A defense attorney should ask:

Did the officer accurately describe the evidence? Were important facts omitted? Did the officer tell the judge something materially different from what the video later shows?

The Blood Draw Must Be Performed in a Medically Acceptable Manner

Even if police had lawful authority to obtain blood, the manner in which it was collected still matters.

In State v. Ravotto, 169 N.J. 227 (2001), the New Jersey Supreme Court suppressed blood evidence where the degree of force used during the draw was unreasonable.

The collection procedure itself may also affect evidentiary reliability.

The State may need testimony concerning:

• who drew the blood;
• whether the person was qualified to do so;
• when and where the sample was collected;
• the collection equipment used;
• whether the specimen was properly labeled and sealed;
• and whether accepted medical procedures were followed.

New Jersey courts have specifically recognized the importance of the blood-draw witness in establishing that proper collection procedures were followed. For example, later appellate authority discussing State v. Renshaw, 390 N.J. Super. 456 (App. Div. 2007) noted that errors in collection can potentially affect the reliability of the BAC result.

 A Nurse Certification Does Not Replace Live Testimony

A police blood kit may contain a certification signed by the nurse or medical professional who performed the draw.

That certification can address important facts concerning the identity of the patient, the time of collection, and whether the blood was drawn in a medically acceptable manner.

But when a certification is created for use in a prosecution, confrontation rights can become important.

In State v. Renshaw, the Appellate Division addressed the testimonial nature of a blood-draw certification prepared for law-enforcement purposes. A defendant may be entitled to cross-examine the person who made those factual assertions rather than having the State simply substitute the certificate for testimony.

Chain of Custody: Can the State Account for the Lab Sample?

After collection, the prosecution must be able to connect the specimen taken from the defendant to the specimen tested in the laboratory.

The defense should trace the sample through:

collection → labeling → sealing → storage → transportation → laboratory receipt → testing → return to police

Important questions include who handled the specimen, when it changed possession, whether seals remained intact, whether identifying numbers match, and whether there are unexplained gaps or discrepancies.

Not every clerical irregularity makes evidence inadmissible. The real issue is whether the State can establish reasonable assurance that the tested specimen is the same sample collected from the defendant and remained sufficiently intact for reliable testing.

For more on this issue, see our Chain of Custody & Evidence Audits in New Jersey.

The Laboratory Result Also Requires a Proper Witness

The State still has to establish the forensic testing.

That raises a different question from whether the nurse properly collected the sample.

A toxicology witness may need to explain:

• how the laboratory received and identified the specimen;
• what testing method was used;
• calibration and quality-control procedures;
• whether screening results were confirmed;
• what substances were detected;
• and how the final conclusion was reached.

But every technician who physically touched the sample does not necessarily have to testify.

In State v. Michaels, 219 N.J. 1, 95 (2014), the New Jersey Supreme Court permitted testimony from a qualified laboratory supervisor who independently reviewed the machine-generated testing data and reached his own conclusion.

More recent New Jersey appellate authority has continued to recognize Michaels after the United States Supreme Court’s decision in Smith v. Arizona, while emphasizing that a substitute expert must provide an independent opinion rather than merely act as a mouthpiece for the absent analyst.

A Positive Urine Test Does Not Automatically Prove Impairment

Urine toxicology is particularly important in drug DWI cases because what it proves can be narrower than many people assume.

In State v. Olenowski, 255 N.J. 529 (2023), the New Jersey Supreme Court recognized that drug metabolites may remain detectable in urine long after the impairing effects of the drug have diminished.

A positive urine result may establish prior exposure to a substance.

It may not establish:

when the drug was taken, how much active drug was present while driving, or whether the person was actually impaired at that time.

That distinction is critical when toxicology is being used to corroborate a Drug Recognition Expert evaluation.

For a deeper discussion, see our Challenging Drug-Impairment Evidence in a New Jersey DWI Case.

Timing Can Change the Meaning of the Blood Result

Chemical samples are collected after the alleged driving.

The defense should establish a precise timeline of:

driving → crash or stop → police contact → medical treatment → medication administration → warrant → specimen collection

This is particularly important after an accident.

A hospital may administer medication before law-enforcement blood or urine is collected. A substance appearing in a later toxicology report should not automatically be attributed to pre-driving use if medical records show it was administered during treatment.

Similarly, a substantial gap between operation and specimen collection may affect what can reasonably be inferred from the laboratory result.

Hospital Blood and Police Blood Are Different

After an accident, a hospital may draw blood independently for diagnosis or treatment.

That is different from police directing medical personnel to obtain a specimen specifically for a DWI investigation. Blood samples from the hospital are often times not admissible because of the testing equipment has been found scientifically reliable by the State and court. Also the controlled environment for testing standards is not as stringent as the state and county labs.

The defense should determine:

• who ordered the test;
• why the blood was drawn;
• whether it was part of medical treatment;
• whether law enforcement directed the collection;
• and how police later obtained the hospital records or sample.

Those distinctions can create different search-and-seizure, privacy, evidentiary, and foundational issues.

Frequently Asked Questions About Blood and Urine Evidence

Do police always need a warrant to draw blood in a DWI case?

No. Valid consent or a recognized warrant exception may permit a warrantless draw. But McNeely and State v. Adkins reject an automatic rule that dissipation alone always creates exigent circumstances.

Does the nurse who drew the blood have to testify?

Where the prosecution relies on testimonial assertions made by the collector concerning how the law-enforcement blood draw was performed, confrontation and foundation issues may require live testimony rather than reliance solely on a certification. The precise requirement depends on how the State attempts to introduce the evidence.

Does every laboratory technician have to testify?

No. Under State v. Michaels, 219 N.J. 1 (2014), a properly qualified substitute expert may testify based on independently reviewed machine-generated data and an independently reached opinion. The witness cannot simply repeat another analyst’s testimonial conclusions.

Does a positive urine test prove drug impairment?

No. It may establish drug or metabolite presence but may not establish impairment at the time of driving.

Can chain-of-custody problems affect admissibility?

Yes. Significant deficiencies in identification, sealing, storage, transportation, or laboratory receipt can raise questions about whether the State has adequately authenticated the specimen and established its integrity.

Can the blood-draw warrant itself be challenged?

Yes. The defense can examine the probable-cause basis for the warrant, the accuracy of the officer’s representations, and whether the supporting sworn testimony was properly preserved for review.

Challenging Blood and Urine Evidence in a New Jersey DWI Case

Blood and urine evidence involves much more than the number printed on a laboratory report.

A proper defense should examine the constitutional authority for obtaining the sample, the warrant application, the collection procedure, the collector’s testimony, chain of custody, laboratory methodology, toxicology witness, and the scientific meaning of the final result.

Cases including State v. Ravotto, 169 N.J. 227, 777 A.2d 301 (2001), State v. Renshaw, 390 N.J. Super. 456, 915 A.2d 1081 (App. Div. 2007), State v. Adkins, 221 N.J. 300, 113 A.3d 734 (2015), State v. Michaels, 219 N.J. 1, 95 A.3d 648 (2014), and State v. Olenowski, 255 N.J. 529, 304 A.3d 598 (2023) show why each stage of the process can matter.

William Proetta Criminal Law reviews warrants, blood-draw records, collector certifications, chain-of-custody documents, hospital records, toxicology data, laboratory procedures, body-camera footage, and the witnesses necessary to introduce chemical evidence in New Jersey DWI cases.

If you have been charged with DWI, call (201) 793-8018 in Jersey City law office or (732) 659-9600 in Edison law office for a confidential consultation.

For a complete overview of New Jersey DWI law and defenses, visit our New Jersey DWI Lawyer and Defense Guide.