Examples from the practice
The represented examples were selected randomly from my long-standing practice, and anonymized for reasons, certainly known to you, to an extend, that an inference onto the actual events and the involved persons is no longer possible . The descriptions are supposed to serve only as a reference that the reinvestigation of fires even dating back some time is by any means not that hopeless even if it likes to appear so at a first glance.

Mostly the results of erroneous determination have comprehensive consequences for the involved persons, nevertheless such cases reach only rarely the consciousness of the public as for example in these cases listed under the menu point 'press reports'.
Fire in a car park in a former factory building
In a car park of a former factory building a fire occurred in case of which the building and several vehicles were damaged. One of the tenants of this car park was accused of negligent arson because he had put a charcoal grill into the car park after a barbecue and the grill had possibly not been emptied completely. The ground of the car park was overcast by scattered wood shavings via which a possible fire spreading might have occurred. The fire was investgated by the police with a considerable delay (~weeks). So far the facts seemed to be clear.

As the lawsuit started, the scene of fire has already been cleared away for a long time. The investigation file contained photographs, which an emloyed damage expert of an insurer who was on site shortly after the fire event, had made, and the photographs taken by the police.

Solely based onto the investigation file and the photographs contained therein a correct technical interpretation of the facts could prove unambiguous that the fire could impossibly have come from the grill put in the car park. The defendant therefore was innocent in the sense of the accusation.
A sea container on fire in a spanish harbour
Shortly after the loading of a 40-ton sea container onto a heavy-duty low-loader truck, the container burned still in the harbour area. The fire was registered by the spanish police, but however no investigation was initiated. The witnesses described that they observed a fire which arose from the interior of the container. As this machine of 40 tons was only a small part of a large scale plant that could not be replaced quickly, a fatal situation arose for the supplier of the entire system, since it was impossible to perform the project schedule for the plant due to this event.

The inspection of the photographs of the container made by different persons after the fire and the investigation of the container content in the container, where parts of the container damaged by the fire had already been removed, showed, that the fire definitively did not arise from inside the container. Also the obvious resaying of the testimonies could be clarified perfectly by the determination of the origin of the fire and the resultant fire development. The principal could avert by means of that a threatening high penalty for non-performance.
Fire in a private home
In a private single-family home in a fire occurred in the kitchen of the house in the night after a childs birthday party. The fire was examined by the criminal investigation department and an expert of an expert organization. The result of this investigation was: Outbreak of a fire through negligent disposal of still smoldering tobacco products into a not suitable garbage can

Since the supposed culprit was active in an exposed position, a sentencing because of negligent arson would have caused a defamation next to the already suffered material damage.

The reinvestgation of the fire scene showed that during the first investigation through the criminal investigation department and the expert of the expert organization already the fire patern has been misinterpreted and also other important traces have been overlooked. Already the first short inspection of the fire scene regarding the fire pattern showed that the fire origin could not have been the garbage can in the kitchen. The further investigation of the fire scene and the devices originally placed there resulted then in a technical defect being able to be proved at the electric cooker supply line. The suspect was accordingly completely innocent, which would have never been detected without a thorough reinvestgation of the fire scene.
Fire in the paintshop of a middle-class industrial enterprise
In a paintshop of an industrial enterprise a fire occurred. The paintshop was at the moment of the outbreak of the fire not active since reconstruction tasks at the coating-line were carried out. The investigations of the criminal investigation department and an expert for enamels and colors did not lead to the wanted success.

During the investigation of the fire scene it turned out, that while the reconstruction work on the coating-line a metal support whose inner side showed into the paint booth above the enamel refining dust collector was drilled-through and hot drilling chips fell onto the enamel refining dust, by which the most finely distributed enamel particles were lit. The resposible for the outbreak of the fire was therefore not the operator of the coating-line, but the contractor for the reconstruction work.
Fire in a former farmhouse
A fire of an old farmhouse that has been rebuilt to a residential building. Since it was already the second fire case in this house, the scene of fire was only hardly accessible, a source of fire was not found and the house inhabitants were financially badly set and at the moment of the outbreak of fire either not at home, the 'cause of fire' was quite quickly certain for the criminal investigation department: Arson by the owner. Relieving facts were simply not considered. An expert was not consulted.

The thourough reinvestigation turned out a clear origin of fire within the last ceiling to the roof frame work of the house. This origin of fire was not recognized by the criminal investigation department and not examined thus either. The origin of fire was covered by a big pile of paper bags lying on top of each other, which were also still unburned to a large part, from the completely burned down roof timbering, so that a fire spread from the roof frame work into the ceiling could be excluded with a probability right next to safety and that the ceiling glowing-fire had to be therefore causal for the fire. An arson could be excluded by that with extensive safety.
Fire in a joinery
The fire in a joinery resulted in a legal dispute between the building proprietor and the operator of the joinery which had rented the business room, who would have to account for the fire ultimately. Since the floor of the building in the range of an electrical saw was covered with considerable amounts of wood shavings at the moment of the outbreak of the fire, and the investigation of the criminal investigation department gave no concrete results, the operator of the joinery was charged with negligence since he had not disposed the wood shavings immediately on completion of the work. Thus because the criminal investigation department stated that it could be possible and under circumstances to a certain amount probable that the fire was caused by hot metal particles injected into the wood shavings bundle around the saw during the sawing process.

A reinvestigation during a judicial hearing at the fire scene approx. 1 year after the fire event showed up a technological defect on an electrical line of the building installation that could still be proved.
Fire in a dwelling house with thermal solar system
The fire in the attic storey of a dwelling house could not be clarified through the criminal investigation department unambiguously. As a possible fire cause the thermal solar system installed in this range of the roof came into consideration.

By means of the photographs contained in the investigation file, could through a reconstruction of the physical conditions over a year after the fire event the thermal solar system be excluded as a fire triggering component and thus the fitter of the system be relieved.