A rooftop fire at a Lineage cold-storage facility in Boyle Heights in June 2026 illustrates how quickly a PV-system fire becomes a causation fight. According to news reports, Lineage, the warehouse operator, has said the fire started on the roof while a subcontractor working on the rooftop solar array was performing testing, and has pointed to the array's owner, Altus Power. Altus Power has said publicly that the cause of the fire "has yet to be determined" and that it is cooperating with authorities, who were still investigating as of late June 2026. When parties dispute whether a photovoltaic system ignited a fire or merely sat near where it began, the case stops being about damages and turns into a question of physics. That is where a solar fire expert witness does the work.
This is a narrow corner of fire engineering, and few directories or referral networks track it well. Most fire-cause experts come from a building or structural background. Fewer can read an inverter fault log, trace a DC string back to its combiner, or explain to a jury why an arc fault leaves a different signature than an overloaded breaker. If your case turns on a rooftop array, the gap between a general fire investigator and a PV-literate electrical engineer can decide the outcome.
Why rooftop solar cases need a different kind of fire expert
A conventional electrical fire usually involves AC circuits, branch wiring, and components a seasoned investigator has seen for decades. A rooftop solar system works differently. The panels generate direct current, often at voltages high enough to sustain an arc that an AC breaker would never trip. The current flows through string wiring, combiner boxes, rapid-shutdown devices, and one or more inverters before it ever touches the building's conventional electrical system. Each of those components fails in its own way, and each leaves its own evidence.
That matters because DC arc faults behave unlike anything in standard residential or commercial wiring. A DC arc does not self-extinguish the way an AC arc can at the zero-crossing point of the waveform. It can hold, glow, and ignite nearby material while the rest of the system reads as normal. An expert who misses this distinction may look at an intact inverter and conclude the array was not at fault, when the real story is upstream in a corroded connector or a poorly torqued lug.
So the threshold question in any rooftop solar fire investigation is not just "was it electrical." It is "which part of the PV system, under what condition, at what point in time." A solar fire expert witness answers that with engineering, not assumption.
How the expert traces an ignition point
Good origin-and-cause work on a solar array follows a disciplined sequence, and you want to understand it well enough to test it on the stand, whether the expert is yours or the other side's.
It generally moves through these stages:
- Establish the area of origin. Burn patterns, char depth, and the direction of fire spread narrow the roof to a zone before anyone touches a wire. If one party's theory puts origin in one place and the physical patterns point somewhere else, that conflict is worth probing early.
- Map the system as built. Single-line diagrams, panel layouts, string assignments, and as-installed photos let the expert reconstruct how current actually moved. Cases often turn on the difference between the system as designed and the system as installed.
- Isolate the suspect component. Connectors, combiner boxes, inverters, and rapid-shutdown units each carry diagnostic clues. Heat damage, melt patterns, and the presence or absence of beading on conductors point toward or away from each candidate.
- Distinguish cause from victim. A component can be destroyed by a fire it did not start. Separating the ignition source from collateral damage is the hardest and most contested part of the analysis.
- Reconcile the data. Inverter logs, monitoring data, and utility records can timestamp anomalies. When the physical evidence and the electronic record agree, the opinion is hard to shake. When they conflict, that is the opening for cross-examination.
The Boyle Heights matter shows the stakes. Where one party alleges that on-site testing of an array contributed to a fire, as reportedly occurred there, opposing counsel needs an expert who can evaluate whether any such testing was sound, whether it could have introduced or aggravated a fault, and whether the conclusions actually follow from the data, rather than assuming a cause the investigators themselves have not yet established. That is a question of method, and method is where credible experts separate from advocates.
Arc faults, inverter failures, and DC wiring as evidence
Three failure modes account for most PV ignition theories, and each leaves something a qualified expert can read.
Arc faults come in series and parallel forms. A series arc often traces to a loose or degraded connection, a backed-out terminal, or a connector that was never fully seated. A parallel arc usually involves insulation breakdown between conductors. The physical signatures differ, and so do the upstream causes, which can implicate installation workmanship, product defect, or maintenance.
Inverter failures can ignite directly or can mask a problem elsewhere. An expert examines whether the unit failed on its own, whether it responded correctly to an upstream fault, and whether its logs captured the event. Firmware behavior and protective-function performance are fair game.
DC wiring and connectors cause many rooftop fires without drawing attention. Undersized conductors, thermal cycling, water intrusion, and mismatched connector brands all create resistance, and resistance creates heat. A solar fire expert witness who can connect a specific installation choice to a specific thermal failure gives you something a jury can follow.
Choosing and qualifying the expert
Credentials in this space are specific. Look for an electrical engineering background paired with hands-on PV experience, familiarity with the fire investigation methodology your jurisdiction expects, and a record of distinguishing cause from collateral damage rather than simply blaming the nearest component. Ask how many rooftop solar matters they have actually worked, not just how many fire cases overall. Ask whether they can read inverter logs themselves or rely on someone else to interpret them.
Then pressure-test independence. An expert who reaches a clean, defensible conclusion that happens to hurt your case is more valuable in the long run than one who tells you what you want to hear and crumbles on cross. The methodology should be reproducible and tied to the evidence, not to the retainer.
The practical takeaway
If your matter involves a rooftop array and the parties disagree on cause, do not default to a general fire investigator and hope they can grow into the photovoltaic side. The questions that decide these cases (DC arc behavior, inverter response, connector failure, the soundness of any post-fire testing) sit at the intersection of fire science and electrical engineering. Retain someone with both, and retain them early enough to preserve and examine the array before it is altered or scrapped.
When you are sourcing that kind of specialist in California, start with experts who already list their PV and electrical fire experience rather than cold-calling generalists. You can browse fire and explosion engineering experts in our directory to see who works rooftop solar matters and compare their backgrounds before you reach out. This article is general information for litigators, not legal advice.