PLACERVILLE, Calif. — In an interrogation room, the difference between asking a question and trying to force an answer can determine whether an investigation uncovers the truth — or sends investigators down the wrong path.
That distinction has become a defining issue in El Dorado County District Attorney Vern Pierson’s efforts to change how law enforcement officers conduct interviews.
Five years after the introduction of the Principles on Effective Interviewing for Investigations and Information Gathering, commonly known as the Méndez Principles, the international framework has become part of a broader movement toward science-based, rapport-driven interviewing.
The principles were published in 2021 after four years of work involving experts in law enforcement, psychology, criminology, human rights and other fields. Their central premise is straightforward: investigators should seek accurate and reliable information rather than make obtaining a confession the primary objective.
For El Dorado County, the issue is more than an international debate over policing practices. It has roots in one of the county’s most consequential wrongful-conviction cases.
A lesson from the Ricky Davis case
In 1985, newspaper columnist Jane Hylton was stabbed to death at her El Dorado County home. The case remained unsolved for years before investigators reopened it and questioned people connected to the crime.
Ricky Davis ultimately was convicted of Hylton’s murder and spent roughly 15 years in prison maintaining that he was innocent.
In 2020, DNA evidence and genetic genealogy identified another suspect. Pierson’s office moved to dismiss the charges against Davis and sought a finding of factual innocence. Davis was released after the court granted the request.
Pierson has described the experience as a turning point in his approach to interrogation.
The case also involved Connie Dahl, who falsely confessed to helping Davis commit the killing. Dahl’s conviction was vacated in 2024 after Pierson’s office concluded that she and Davis had not committed the crime.
The case convinced Pierson that traditional interrogation practices could become dangerous when investigators began with an assumption of guilt and then used deception or psychological pressure to obtain a confession.
“There’s a better, more effective and ethical way for law enforcement to conduct interviews,” Pierson said.
From confession hunting to information gathering
Traditional interrogation models, including practices commonly associated with the Reid Technique, have historically emphasized confronting suspects, presenting investigators’ theories of the crime and attempting to overcome resistance until a confession is obtained.
Critics of those methods argue that deception, pressure and prolonged confrontation can increase the possibility of false confessions, particularly when investigators become committed to an incorrect theory of a case.
The Méndez Principles take a different approach.
Rather than treating an interview as a contest between an investigator and a suspect, the framework emphasizes preparation, rapport, open communication, active listening, procedural safeguards and the collection of information that can be independently verified.
The principles state that accurate information and respect for human rights are not competing objectives. Research cited by the authors supports rapport-based, noncoercive approaches to information gathering and rejects torture and ill-treatment as ineffective and counterproductive.
That philosophy also underlies science-based interviewing programs such as ORBIT, which use research into interviewer behavior and rapport to improve engagement and information yield. A recent five-year assessment of the Méndez Principles reported that ORBIT research has analyzed more than 2,000 hours of real-world interviews.
California becomes a testing ground
California has become one of the most significant American examples of the shift.
In 2024, the California Commission on Peace Officer Standards and Training, commonly known as POST, issued guidance requiring certified interviewing programs to demonstrate an empirical foundation and show that they do not teach methods associated with false confessions.
The standards prohibit threats, physical harm, deception and psychologically manipulative tactics in the certified interviewing curriculum. According to a July 2026 assessment of the Méndez Principles, more than 5,500 officers had been trained in science-based interviewing in California during the preceding three years.
Pierson has played a role in that transition.
The El Dorado County District Attorney’s Office says Pierson began pushing for changes in investigative interviewing after the Davis case and has since promoted science-based interviewing as an alternative to coercive interrogation. His office reports that he has hosted training sessions involving 107 California law enforcement agencies and seven agencies in other states and countries.
The effort is significant because changing interrogation practices is not simply a matter of issuing a new policy. It requires changing how detectives are trained to think about interviews in the first place.
A prosecutor’s policy with local consequences
Pierson took the issue beyond training.
In September 2022, his office announced a policy limiting the filing of criminal charges when the primary evidence against a suspect consists of a confession obtained through threats, deception or psychologically manipulative interrogation tactics.
The policy reflects a basic prosecutorial question: What is the quality of the evidence?
A confession may appear powerful, but if investigators obtained it by supplying false information, threatening consequences or psychologically manipulating a suspect into accepting an investigator’s theory, its reliability becomes a central concern.
Pierson has argued that prosecutors have an obligation to scrutinize the manner in which evidence was obtained, not simply the evidence’s apparent usefulness.
That position puts El Dorado County at the center of a broader national debate about the future of police interrogation.
Why false confessions matter to public safety
The argument for science-based interviewing is not limited to protecting innocent suspects.
A false confession can create a second public-safety problem: It can cause investigators to stop looking for the person who actually committed the crime.
The Davis case illustrates that danger. Davis spent years incarcerated before new forensic evidence established that someone else was responsible for Hylton’s murder. The investigation ultimately identified another suspect and resulted in a prosecution for the crime.
Nationally, false confessions have also appeared repeatedly in wrongful-conviction cases. The Los Angeles Times reported that false confessions have been involved in hundreds of exonerations since 1989 and noted research showing that, in a significant number of those cases, the actual perpetrators later were identified.
For law enforcement, the implication is consequential: An unreliable confession does not merely threaten the rights of the person being questioned. It can compromise the entire investigation.
The Méndez Principles reach beyond El Dorado County
The Méndez Principles are not California law, nor are they legally binding. They are a professional framework intended to influence how governments and investigators gather information while protecting legal and human-rights safeguards.
Five years after their launch, the principles have been translated into 24 languages and are being implemented through training, research, professional standards and institutional reforms in jurisdictions around the world. The United Nations also has incorporated investigative-interviewing concepts consistent with the principles into its training and guidance materials.
California’s experience is particularly notable because the transition is being pursued through professional standards and law-enforcement training rather than relying solely on legislation.
A 2021 California bill that would have required science-based investigative-interviewing training statewide was vetoed by Gov. Gavin Newsom. The state subsequently moved toward POST-developed training standards instead.
That makes the California model an unusual test of whether professional regulation and training can change a policing culture that has relied on interrogation practices for generations.
What it means for El Dorado County
For residents of Placerville, El Dorado Hills, Cameron Park, South Lake Tahoe and communities throughout the county, the issue ultimately comes down to the reliability of the criminal justice system.
A detective’s job is not simply to obtain an admission. It is to determine what happened, identify who was responsible and build evidence capable of surviving scrutiny in court.
That distinction is at the heart of Pierson’s advocacy.
His experience with the Davis and Dahl cases transformed a local wrongful-conviction investigation into a much broader campaign to change investigative interviewing. The effort now extends from El Dorado County law enforcement training to California’s POST standards and the international conversation surrounding the Méndez Principles.
The five-year assessment published in July describes the central lesson succinctly: effective interviewing does not require choosing between obtaining information and respecting rights. The evidence increasingly suggests that the two goals can reinforce each other.
For a prosecutor whose office once had to confront the consequences of a wrongful conviction, that distinction is not theoretical.
It is a lesson learned from an El Dorado County murder case — and one Pierson is now trying to ensure investigators do not have to learn the same lesson the hard way.
Sources and public documents:
El Dorado County District Attorney’s Office — Michael Green Sentenced / New DA Interrogation Policy
The Méndez Principles — full 2021 document
Just Security — “Effective Interviewing, Not Torture: Lessons from the Méndez Principles Five Years On”
Northern California Innocence Project — Ricky Davis case history
