The Absent Analyst: Confrontation and Chain of Custody in a DUI Blood Case
At 1:42 a.m. on March 9, Officer Dane Whitfield stopped Marisol Vega after she drifted across the center line twice. Vega smelled of alcohol, failed the walk-and-turn, and gave a breath sample of 0.094. She then consented to a blood draw at 2:55 a.m.; the sample was logged into the Colorado Bureau of Investigation laboratory the next morning with a two-day gap in the refrigerator temperature log. The lab report shows 0.11 BAC and is signed under penalty of perjury by analyst Sofia Reyes, who performed the test. Reyes is now on military deployment and unavailable. The prosecution intends to prove the report through (1) Reyes's affidavit and (2) testimony from analyst Owen Pratt, who reviewed Reyes's data and raw machine output but did not run the test or observe it. Defense counsel objects on confrontation and chain-of-custody grounds. The court asks for your analysis before ruling.
1. Should the court sustain Vega's Confrontation Clause objection to Reyes's sworn lab report? Explain the constitutional rule and its application.
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Rule. The Confrontation Clause bars admission of a testimonial statement by a witness who does not appear at trial unless the witness is unavailable and the defendant had a prior opportunity to cross-examine. A lab certificate prepared for use in a criminal prosecution is testimonial; it is the functional equivalent of live testimony, not a neutral business record.
Application. Reyes's report was generated after a police-initiated blood draw, states a BAC result, is sworn under penalty of perjury, and exists to prove an element of the DUI offense. That is the core of a testimonial statement. The business-records exception does not override the Clause when the statement is testimonial, so the prosecution cannot launder the report through a records custodian. Reyes's unavailability is only half of the required showing; Vega never had an opportunity to cross-examine her, and there is no evidence of forfeiture by wrongdoing.
Conclusion. The objection should be sustained as to the affidavit. The practical consequence is that the prosecution must produce Reyes or, if she is genuinely unavailable, seek a continuance rather than substitute a paper certificate.
2. Can the prosecution prove the 0.11 BAC through Owen Pratt's testimony about Reyes's data and the machine output?
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Rule. A surrogate analyst who neither performed nor observed the test cannot testify in place of the analyst who certified the result. The defendant's right is to cross-examine the person who made the testimonial assertion, not a reviewer who repeats it.
Application. Pratt reviewed Reyes's data and raw machine output, but he did not run the test or watch it being run. If he testifies that the report shows 0.11, he is merely a conduit for Reyes's assertion, which is exactly what the Clause forbids. The analysis changes only if Pratt offers an independent opinion: for example, if he independently interprets the chromatogram and reaches his own conclusion without relying on Reyes's report, or if he personally ran a second test on the same sample. Even then, the report itself remains inadmissible, and the prosecution must lay a foundation for the underlying data.
Conclusion. Pratt cannot prove the 0.11 result by narrating Reyes's work. The court should exclude both the report and any testimony that repeats its contents.
3. How should the court handle the two-day gap in the refrigerator temperature log, and does the earlier 0.094 breath result change the analysis?
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Chain of custody is a foundation issue, not a constitutional one. The proponent must show it is reasonably probable that the sample is what it purports to be and has not been altered. A two-day gap in the temperature log weakens that showing but does not automatically require exclusion; the court has discretion to admit if the sample was sealed, labeled, and accounted for. The gap is fair ground for cross-examination on degradation or fermentation, which could produce a falsely high result.
The breath result is a fact for the jury. A 0.094 breath sample and a 0.11 blood sample are not irreconcilable - different tests, different times, different margins of error - and the discrepancy goes to weight, not admissibility. It may support an argument about rising or falling alcohol concentration, but it does not bar the blood evidence.
Practical point. The chain-of-custody ruling may be moot unless the sample itself is retested or Reyes appears. If the report is excluded, the remaining question is whether the breath result alone supports the charge.