When experts merely state the obvious without grounding their testimony in known facts, their testimony is typically excluded as being unhelpful to the jury. At a preliminary hearing in a criminal prosecution, however, decisions are made by a judge rather than a jury. Judges tend to be more lax about admitting expert testimony when they act as the decisionmaker.

It may nevertheless be worth questioning the value of an arson investigator’s expert opinion that a dumpster fire was probably started by a lighter or matches. Flames start most dumpster fires, but in the absence of evidence connecting a flame to a defendant, the expert opinion tells the judge nothing that the judge doesn’t already know.

Arson Prosecution

Efren Uribe is homeless. He was charged with arson in Sacramento County, California. Prosecutors allege that he used a lighter to start a fire in a dumpster and that he did so intentionally.

The dumpster is one that Uribe visits regularly in a search for food. He was seen entering the dumpster and then climbing out of it on the day of the fire. A convenience store employee had seen Uribe search the dumpster for food on multiple occasions during the previous two or three years.

There is no dispute that a fire began in the dumpster a few minutes after Uribe climbed out of it. No video captured the cause of the fire. No eyewitness saw anyone start the fire. The prosecution therefore relied on expert testimony to make a case against Uribe at his preliminary hearing.

Expert Testimony

The arson investigator, Brandon Lynch, works for the Sacramento Fire Department. His job is to investigate the origin of fires. He has done so on dozens of occasions. The court allowed him to testify as an expert witness.

Lynch testified that the dumpster fire originated from an “open flame device … such as a lighter or potentially matches.” The fact that flames start fires is obvious and uncontroversial. Electrical fires don’t occur in dumpsters. Nor was the dumpster struck by lightning.

Yet fires do not need to be started by lighters or matches. As Lynch admitted on cross-examination, someone could have tossed a cigarette into the dumpster, igniting its contents. A heated Sterno can or some other hot object tossed into the dumpster might also have started the fire.

In short, the arson investigator had no evidence as to how the fire started. His opinion that it was probably started by a flame is one that the judge could just as easily have formed without the benefit of expert testimony.

The prosecutor apparently believed that Lynch’s testimony was significant because Uribe had three lighters in his possession when the police arrested him. Yet Lynch’s testimony that the fire was caused by “a lighter or potentially matches,” while carefully phrased to make it seem that a lighter was the more likely source of the flame, added little to the prosecution’s case.

Uribe might have used a lighter to start the fire while he was inside the dumpster, but nobody saw him do so. Lynch admitted that he could think of no reason why Uribe would want to set the dumpster on fire. An expert opinion that “lighters can start fires” says nothing about whether this fire was started by a lighter, much less by one of Uribe’s lighters.

Hearing Outcome

A preliminary hearing is held to determine whether the prosecution has sufficient evidence to allow the case to proceed to trial. Prosecutors face a low standard of proof at a preliminary hearing. The judge who presides does not evaluate the credibility of witnesses. If the evidence that a jury could believe to be true makes it probable that the defendant committed a crime, the case will proceed to trial.

In light of that low standard, the judge allowed the case to proceed to trial. Whether the arson investigator would be permitted to render the same unhelpful expert opinions at trial is unclear. Given the gaps in the testimony provided by its expert witness, however, the prosecution may decide that it lacks the evidence it needs to meet the trial standard of proof beyond a reasonable doubt. Uribe’s prosecution is a reminder that expert opinions cannot salvage a weak case when the opinions are grounded on speculation rather than evidence.