## Facts

- Robert Hernandez led Albuquerque police on a high-speed chase that ended when he struck a lamppost and hit a wall.
- Hernandez claimed that after officers took him to the ground and handcuffed him, Officer Tom Benard struck him in the back of the head with an asp (a telescoping police baton).
- Photographs taken at the scene showed blood pooling and spatter pointing away from Hernandez.
- Emergency-room paperwork described a head laceration attributed to blunt trauma; later photographs after cleaning showed a wound of roughly one-half inch on the back of Hernandez’s head.
- Hernandez sued Benard and the City of Albuquerque for assault and battery and for use of excessive force.
- Hernandez retained Dr. Alan Watts, a physicist, to offer opinions that (1) the wound was consistent with a blow from an asp and (2) the blood pattern was consistent with at least a second blow.
- Watts had substantial work history with force analysis, shock physics, impact damage effects, and biomechanics, but he had no medical training, no forensic pathology training, and no law-enforcement background; he had never seen anyone struck with an asp.
- Watts’s proposed opinions drew in part from his reading on topics such as swing speeds (e.g., baseball-bat literature), medical sources addressing forces and instruments that can cause lacerations, and forensic sources addressing blood spatter analysis.
- Before trial, defendants moved to exclude Watts’s testimony, arguing he lacked qualifications for key opinions and that the testimony would not assist the jury.

## Issues

1. Whether a physicist with a background in force and biomechanics is qualified under Federal Rule of Evidence 702 to opine that a specific head laceration was caused by an asp and that photographed blood patterns indicate multiple blows.
2. Whether, under Rule 702 and the Daubert/Kumho Tire gatekeeping framework, Watts’s proposed opinions were sufficiently reliable and helpful to the jury, or instead went beyond the subjects for which he was shown to have the necessary training and experience.

## Decision

- The court granted the motion in part and denied it in part.
- The court allowed Watts to testify about physics and biomechanics topics within his demonstrated background, including force and mechanical aspects of impact scenarios.
- The court excluded opinions that amounted to medical diagnosis or medical causation, as well as specialized forensic blood-spatter conclusions and law-enforcement/procedure opinions that were outside Watts’s training and experience.
- The case proceeded with Watts’s testimony limited to the areas the court found fit Rule 702.

## Legal Principles

- Federal Rule of Evidence 702 permits opinion testimony only when the witness is qualified by knowledge, skill, experience, training, or education, and when the testimony is both reliable and helpful to the factfinder.
- Under Daubert and Kumho Tire, the trial court acts as gatekeeper for all Rule 702 testimony, ensuring an adequate match between the witness’s qualifications, the methods used, and the opinions offered.
- Qualification is opinion-specific; a witness may be qualified to address certain technical subjects yet unqualified to offer opinions that require different professional training (such as medicine, pathology, or specialized forensic interpretation).
- Courts may admit part of an expert’s proposed testimony and exclude other parts where the proponent has not shown reliable methods and adequate qualification for the particular conclusions.

## Conclusion

Hernandez v. City of Albuquerque held that a physicist could testify about force and biomechanics relevant to an alleged baton strike, but could not extend that testimony into medical causation, blood-spatter interpretation, or police-procedure conclusions without the specialized training and experience required by Rule 702.


Hernandez v. City of Albuquerque, 2004 WL 5520000 (2004)