Our calculations were based on both the fluctuating daily temperatures of the weather station 6.8 km away from the uncle’s home and constant temperatures, e.g., 15 °C for a possible colonization in the basement room, 24 °C for an indoor room in summer (during the day), and 30 °C daytime temperature for the outdoor colonization in that summer.
Further influences on egg laying and larval development such as rain [20–23], night, and dark conditions [23–29] were disregarded since we were told that the case took place inside or close to the apartment.
Since the maggots of both fly species had reached the third and last stage of development as larvae (before pupation), the larvae could not have developed within one day (e.g., from 23 to 24 July 2022) from oviposition.
We do not know whether the dog was still alive at the time the eggs were laid. It is possible that the dog was neglected and that its wounds were colonized by fly maggots during its lifetime. Lucilia sericata and Sarcophaga argyrostoma are fly species that may colonize living yet neglected bodies [9].
Since we also did not know whether the fly maggots sent in for examination were the oldest maggots that had developed on the dog, the calculated time periods were the minimum development time of the larvae.
The extensive maggot infestation of the oral cavity, the loss of substance on the muzzle due to autolysis, and the strong odor of decomposition before the body was frozen also spoke against the statement that the dog had been healthy and alive on 23 July 2022.
5. Discussion
5.1. Temperatures
Temperature data from the colonization site of the dog were missing. Therefore, the temperatures at which the insects colonized the dog before 24 July 2022 could not be mathematically reconstructed.
If the owner claimed to have visited the dog at about the same time on both days, the maximum PMI hypothesis to test would be approximately 24 h. Assuming the most rapid development rates in the reference papers [17,19], both a 13 mm third larval instar of L. sericata and a 20 mm third larval instar of S. argyrostoma would be too old for the owner to have told the truth, irrespective of the temperatures of the dog carcass.
We decided to use local weather data as well as the most recent developmental data including ADH information to build and check our temperature scenarios (Table 1). Since only one Sarcophaga larva was sent to us and since no recent developmental ADH data were available, we decided to use an older data set for this species that did cover the temperatures we used in our scenarios. This was sufficient because the statement of the owner of the dog was found to be false in all our calculations.
We decided to use the most current data for Lucilia sericata that also include ADH values. Since we observe a massive impact of climate change in Europe, we considered the most modern data to be the most reliable in this particular case. For Sarcophaga argyrostoma, we had to rely on the older data set because the most recent data sets did not cover the temperature ranges that we needed to include in our “check the scenarios” tests.
5.2. Colonization Site of the Dog
It remained unclear whether the dog was colonized inside the house or outside and if windows were closed or not. “Closed” doors in Germany often provide access points for flies, as the adults can squeeze through old keyholes or gaps between the door and the floor.
5.3. Fly Maggots
It is unknown to which colonization wave the fly maggots collected from the dead dog belonged, and especially, if there were older developmental stages of the flies or other insects in the vicinity of the dog. In a strict court room setting, one could also question if the maggots had been alive on the dog. The color changes and conservation state of the maggots did not allow a reliable length measurement. Our measured lengths were minimum lengths.
Concerning a possible lack of information in the scientific literature relating to the variability of the postfeeding stage, we restricted ourselves to the information contained in the sources that we used [17,19]. In the Lucilia larvae as well as the single Sarcophaga larva, we saw three slits in the abdominal (posterior) spiracles. Therefore, we decided that any developmental interval beginning from the transition from larval stage 2 to larval stage 3 until the possible postfeeding stage should be considered. Our minimum developmental estimate already excluded the dog owner’s statement, so in this particular case the question was answered without further examination of a possible postfeeding stage.
We did not aim for the inclusion of larval length data because on the one hand, we wanted to support the veterinary office even though hardly any budget was available and we thought that a discussion about larval lengths might lead to further unpaid work. On the other hand, our approach using scenarios sufficiently covered the questions that we were asked to answer. Since exact environmental information (the dog’s exact place of death, etc.) were unknown, we decided to work on the simplest and safest level so that a possible defense could not use a confusion strategy over numbers. Finally, in our lab, we are hesitant to work in an overprecise manner when larvae arrive in a hardened state. In higher profile cases, we would naturally determine the minimal developmental time from shrunken, hardened maggots, but this case had to be handled under minimalistic conditions, yet with simple and safe conclusions due to the circumstances described above.
5.4. The Dog Owner’s Statement
Strictly speaking, it is unknown whether the dog may have died elsewhere and was then transported to the uncle’s apartment.
5.5. Conclusions
Despite all limitations, our measurements show that the dog could not have been healthily alive on the evening of 23 July 2022. This entomological exclusion matches the observation that the dog’s brain was severely decomposed and largely missing.
The dog was colonized by cadaver flies on the morning of 21 July 2022 at the latest; if the dead or living animal had been in a colder environment than 30 ◦C outside temperature, then colonization could even have taken place much earlier.
In the trial, the court warned the dog owner and ordered her to pay 1200 Euro to a charitable organization. She was banned from keeping animals for one year. After that, the owner may legally own animals again.
Even though the larvae were in poor condition and not all data were available, the question of the animal welfare office could be answered in a useful, legal way. This allowed the office to go on trial.
We believe that this case might remind veterinarians and veterinary pathologists to preserve and document entomological traces in the best possible way. In more difficult cases, a better preservation of the maggots would have been necessary. Here, the relevant question could be answered sufficiently
