Nyabuto trial day 7: Medical examiner describes conducting autopsy on Deputy Bustos

TYLER, Texas (KLTV) - Day seven of the trial of Daniel Nyabuto began with additional questioning of a cellular data analyst and the testimony of a medical examiner.

Nyabuto is charged with intoxication manslaughter in the 2022 death of Deputy Lorenzo Bustos, who was in the final stages of his training with the Smith County Sheriff’s Office.

The defense continued to question Michael Fegely, founder of Cellx Analytics, questioning the validity of his methods as the location shown by phone records is an estimate and not GPS information. Fegely said he has testified over 50 times in court using this technology and said he calculated an estimated speed that Nyabuto was traveling before the crash based on how his phone was moving. He calculated 62 miles-per-hour. On cross-examination, prosecutors showed again that Nyabuto was traveling 65 MPH, as displayed in his airbag control module

Dr. Stephen Hastings, Dallas County Medical Examiner, was called to testify. Hastings conducted an autopsy on Bustos, noting that his time of death was 6:26 a.m. on July 29, 2022. Cause of death was listed as blunt force injury with multiple injuries suffered, including multiple rib and skull fractures. Hastings also noted that Bustos’ brain suffered lacerations and contusions. The state showed photos of the autopsy.

The state then rested its case.

The defense brought in a law enforcement crash expert, Dudley Marchetti, who worked for Dallas PD in crash investigations for 30 years. Marchetti said he does not understand the actions of Bustos on the night of the crash. He claimed that no driver would have been able to see Bustos where he was standing. The defense asked if a person should be punished for hitting Bustos if they could not see the deputy, even if they were going to crash into the vehicle. Marchetti said no.

Marchetti said that Nyabuto was operating his vehicle for transportation, not as a deadly weapon. The state then questioned Machetti, and asked if Bustos would still be alive if Nyabuto had switched lanes. Marchetti said “hypothetically, yes.”

The defense then called forensic toxicology expert Dr. Jimmie Valentine as witness. Valentine is a lifelong academic in the field and has taught at several universities. Valentine said he had concerns over the results of Nyabuto’s BAC test, and cited the way Texas DPS conducts their testing. According to Valentine, DPS laboratories calibrate their machines to fit a wide range of suspected values. He said that in his expert opinion, the machines should be calibrated to a smaller range and then more than two tests should be run.

Valentine went on to say that DPS sets their BAC testing machine with a “zero baseline,” and Valentine said it should be a “free-floating baseline” with other contaminants. Valentine said the integrity of the blood sample matters, and if the sample is compromised then it’s not reliable. According to Valentine, lab procedures should be as simple as possible so that the results can be reproduced consistently. It’s also vital that blood collection tubes be under vacuum to avoid contamination, he said.

Due to these reasons, Valentine said he does not believe Nyabuto’s reported BAC of .144 is accurate.

Valentine said that at Nyabuto’s reported BAC, he would most likely have has slurred speech and an altered gait. He would have had trouble answering or comprehending questions, Valentine said, and the expert never observed the defendant exhibiting euphoric or other behavior to indicate that he was high.

The state then began to cross-examine Valentine, attempting to discredit him based on a number of publications he’s made specifically on defending intoxicated drivers in court. Valentine said he couldn’t necessarily dispute the arresting officer’s testimony that Nyabuto was swaying and slurring at the scene of the crash. Valentine went on to discuss the DPS crime lab, saying it’s less stringent in it’s practice regulations than an employee drug testing lab.

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