Certified Canine “Alerts” (Without a Full “Indication”) Can Establish Probable Cause Under the Totality of the Circumstances

Introduction

In United States v. Conchas-Mancilla (5th Cir. Mar. 31, 2026) (per curiam) (unpublished), the Fifth Circuit affirmed the denial of a motion to suppress cocaine found in a vehicle searched at a routine immigration checkpoint in Sarita, Texas. The key Fourth Amendment issue was whether agents had probable cause to search the car based on a drug-detection dog’s alert behavior—even though the dog did not perform a trained final indication (e.g., sit, scratch).

The parties were the United States (appellee) and Jesus Arturo Conchas-Mancilla (appellant), who challenged the search that led to the discovery of 17.4 kilograms of cocaine hidden in the vehicle’s rear bumper tubing.

Summary of the Opinion

The Fifth Circuit held that, under the totality-of-the-circumstances approach described in Florida v. Harris, the dog’s repeated, strong alerts—combined with the dog’s certification and extensive evidence of reliability—gave agents probable cause to search. The court rejected the argument that probable cause requires a full trained “indication,” and it affirmed the district court’s factual findings crediting testimony that the dog “alerted without a doubt.”

Analysis

Precedents Cited

  • United States v. Alvarez, 40 F.4th 339 (5th Cir. 2022): Supplied the review framework—facts for clear error, law de novo—and the rule that evidence is viewed in the light most favorable to the prevailing party (here, the Government). The panel used this lens when evaluating competing interpretations of the dog’s behavior.
  • United States v. Zavala, 541 F.3d 562 (5th Cir. 2008): Reinforced that whether probable cause exists is a legal conclusion reviewed de novo, allowing the Fifth Circuit to independently apply Harris to the facts found by the district court.
  • United States v. Outlaw, 319 F.3d 701 (5th Cir. 2003): Distinguished factual findings (whether the dog alerted; reliability) from the legal probable-cause determination. This helped the panel treat “alert occurred” and “dog reliable” as factual matters entitled to deference.
  • United States v. Gibbs, 421 F.3d 352 (5th Cir. 2005) (quoting United States v. Santiago, 410 F.3d 193 (5th Cir. 2005)): Emphasized that clear-error review is “particularly strong” when the district court relied on live testimony. That principle supported deference to the trial judge’s credibility determinations about the canine handler and training specialist.
  • United States v. Keller, 123 F.4th 264 (5th Cir. 2024): Provided the terminology distinction between “alert” (instinctual change in posture) and “indication” (trained final response). Conchas-Mancilla leaned heavily on a footnote in Keller, but the panel read Keller as consistent with Harris and as rejecting rigid rules. Keller was treated as explaining that an indication can be near-dispositive, not that an alert can never suffice.
  • United States v. Clayton, 374 F. App'x 497 (5th Cir. 2010): Quoted for the proposition that Fourth Amendment doctrine does not demand a “specific and consistent code” for canine signaling. This undermined the appellant’s attempt to elevate “indication” into a constitutional requirement.
  • Florida v. Harris, 568 U.S. 237 (2013): The central controlling precedent. The panel applied Harris’s common-sense “totality of the circumstances” test and its presumption that a certified dog’s alert can supply probable cause (subject to conflicting evidence). Harris also supported the panel’s view that courts should not “split hairs” over labels when the overall circumstances demonstrate a reliable odor detection.
  • United States v. Martinez, 102 F.4th 677 (5th Cir. 2024); United States v. Shen, 749 F. App'x 256 (5th Cir. 2018); and United States v. Clayton, 374 F. App'x 497 (5th Cir. 2010): Cited to show the Fifth Circuit has “repeatedly held” that an alert short of a full indication can provide probable cause, reinforcing that the appellant’s proposed alert/indication bright-line rule conflicts with circuit practice.
  • United States v. Sanchez-Pena, 336 F.3d 431 (5th Cir. 2003): Used to confirm that an indication reliably supplies probable cause; the panel treated this as complementary to (not exclusive of) alert-based probable cause.
  • United States v. Villafranco-Elizondo, 897 F.3d 635 (5th Cir. 2018): Though addressing a different canine-probable-cause angle, it was cited to reinforce the broader theme that canine signaling is not governed by rigid, mechanistic requirements.

Legal Reasoning

The court’s reasoning proceeds in three moves:

  1. Reject a categorical “indication-or-bust” rule. The panel framed the Fourth Amendment inquiry per Florida v. Harris: whether “all the facts surrounding [the] dog’s alert,” viewed with common sense, would lead a reasonably prudent person to believe a search would reveal contraband. It stressed that Harris does not require a particular “code” of canine behavior, and the Fifth Circuit’s own cases do not demand a “full and final alert” before probable cause exists.
  2. Defer to the district court’s factfinding on alert and reliability. Applying United States v. Outlaw and the heightened deference emphasized in United States v. Gibbs (and United States v. Santiago), the panel accepted the trial court’s findings that the dog alerted and that the handler and training specialist credibly interpreted the behavior as an alert.
  3. Apply Harris’s totality test to the specific record. The panel found probable cause especially strong because (a) the dog was certified by U.S. Customs and Border Protection, supporting the Harris presumption of reliability; (b) the record described the dog as unusually successful and not requiring remedial training; and (c) the dog twice alerted at the same location (rear bumper), and the subsequent search confirmed cocaine hidden precisely there. Even without a trained “indication,” the court concluded the alerts were not ambiguous in context.

Impact

Although the opinion is not designated for publication (5th Cir. R. 47.5), it illustrates how Fifth Circuit panels are likely to analyze canine-sniff probable cause disputes after Florida v. Harris and United States v. Keller:

  • Alerts can suffice. Litigants should expect courts to treat “alert vs. indication” as descriptive terminology rather than a constitutional dividing line.
  • Reliability evidence matters. Certification plus demonstrated performance can substantially strengthen probable cause; conversely, defendants will need concrete “conflicting evidence” (training deficiencies, false-alert patterns, cueing, flawed certification) to erode the Harris presumption.
  • Trial-court credibility determinations are hard to overturn. Where the ruling rests on live testimony about canine behavior, appellate review is especially deferential.

Complex Concepts Simplified

  • Probable cause: A practical, common-sense standard—whether it is reasonable to think evidence of a crime will be found in the place to be searched; it is less demanding than proof beyond a reasonable doubt.
  • Free-air sniff: A dog sniff of the exterior air around a vehicle; here it occurred at a checkpoint before the search.
  • Alert vs. indication (Border Patrol terms): An alert is an instinctive behavioral change upon encountering an odor; an indication is a trained final response (sit/scratch/etc.). The court treated both as inputs to the same totality-of-the-circumstances probable-cause analysis.
  • Motion to suppress: A request to exclude evidence obtained in violation of the Fourth Amendment; if granted, the government may be unable to use the drugs or derivative statements at trial.
  • Standards of review (clear error vs. de novo): Appellate courts defer heavily to trial-court fact findings (clear error) but independently decide legal questions like probable cause (de novo).

Conclusion

United States v. Conchas-Mancilla reinforces a practical Fourth Amendment rule derived from Florida v. Harris: a certified, reliable drug dog’s alert—even without a full trained indication—may establish probable cause when the totality of the circumstances supports a common-sense inference that contraband is present. The decision’s broader significance lies in its rejection of mechanistic canine-behavior thresholds and its emphasis on reliability evidence and trial-court credibility determinations in suppression litigation.