Source: Rom J Leg Med (2025) 33: 210–215; DOI: 10.4323/rjlm.2025.210
By Kristina Baumjohann, Mark Benecke
Abstract: In an apartment, the previous tenant had died. His decomposition fluid had seeped into the wooden floorboards of the old building over a long period of time. The next tenant sent us samples of the wood and various insects that had come from the apartments’ floor. There was a noticeable decomposition odor in the apartment. The landlord wanted to immediately sublet the apartment and denied both the presence of the decomposition smell and a connection between this and the presence of the insects. We had to clarify whether the discoloration in the wooden floor was caused by seepage of corpse fluids and whether the appearance of the insects was related to the deceased previous tenant. The species composition of the insects and an ammonia test was indicative of the presence of at least decomposition fluid which may have come from a corpse.
Keywords: forensic entomology, forensic biology, stains, insects, decomposition.
CASE DESCRIPTION
The client had rented an apartment in which the previous tenant had died and been lying dead on the wooden floor in the apartment for a long time. The wooden floorboards there were discolored. There was a noticeable corpse odor in the apartment. Our client repeatedly found various insects in the now empty apartment. The landlord did not want to commission any extensive renovation work, as is usual in the city in question, owing to the housing shortage – he wanted to rent the apartment out again immediately. He stated that: - There was no corpse odor; only a smell of sanded wood. - The visible stains could have been caused by any liquid, e.g. coffee. - The flies found in the apartment had come from outside by chance, had not developed in the apartment and were not attracted by the decomposition smell of the deceased. Insect and wood samples were obtained to clarify whether the discoloration in the wooden floor was caused by corpse fluids seeping into it and whether the occurrence of the insects was related to the deceased previous tenant. We were able to establish a connection between the appearance of the insects and the corpse fluid that leaked and seeped into the wooden floor (and far below).
MATERIAL AND METHODS
Insects
Insects were examined with a stereomicroscope binocular (Leica MZ12.5, max. 100x) and identification keys [1-5].
Floorboards/odor
Due to the time pressure and suffering of those affected, it was not possible for us to inspect and take samples on site. However, we had photos and a video of the apartment in very good quality. The samples of the wooden floorboards were each packed airtight in three-layer Ziploc bags, with another small airtight bag with wooden material inside.
Each sample of those samples was sent to us in a glass jar (Fig. 1). Some of the wood material had a distinctly dark, charred-looking discoloration (Fig. 2). The wood samples consisted of smaller and slightly larger pieces of wood (Fig. 3).
Ammonia test
A rapid ammonia test (Bosike/Like Sun Company, Essen, Germany) was conducted to exclude coffee and as an indication of putrification liquid [6, 7]. Therefore, a small piece of a darkly discolored area of the wooden floor was swirled in 3 ml of sterile water (disposable vial, AddiPak Company), and put in a sterile, DNA-free centrifuge tube (Greiner Company) for a few minutes (Fig. 4). The ammonia test strip was dipped into it.
RESULTS
Insects
The samples contained the following insect groups and species: - Flesh flies of the genus Sarcophaga spec. (Fig. 5); - Blow fly of the species Calliphora vicina (Fig. 6); - Carpet beetles (skin beetles), probably of the genera Attagenus spec. and Anthrenus spec. (Dermestidae) (Fig. 7); - Larder beetle larvae (Dermestidae) (Fig. 8); - Chalcid wasps, probably of the family Torymidae (Chalcidoidea) (Fig. 9).
Flesh flies (n = 56) were most prevalent in the samples, followed by carpet beetles (n = 41) and chalcid wasps (n = 9), while only one blow fly was present (Table 1). The skin beetle larvae were numerous and we did not count them. Apart from the chalcid wasps, all insects found in the samples are associated with decomposition processes of human and animal bodies [8-11].
While blow flies visit dead bodies in earlier stages of decomposition [12, 13], flesh flies colonize corpses during the entire decomposition process [14-22]. In large cities, this is particularly true for corpses found in apartments.
Carpet and/or skin beetles and their larvae occur in later stages of decay (desiccation) and prefer drying organic tissue (including mummies, stuffed animals, etc.) on which they feed [23-26]. Chalcid wasps are predators of other insects that colonize corpses, such as the blow flies and flesh flies found in the samples [27]. They only appear later during the course of corpse colonization, as they do not colonize the corpse as such, but animals living on the corpse.
Individual adult, dead flies showed holes and erosions, which may have been caused by skin beetles and chalcid wasps. This is a further indication of prolonged colonization and/or the prolonged presence of insects colonizing corpses and attracted by the odor of corpses (Fig. 10).
Odor
As soon as the glass lids (i.e. the outermost packaging of the multi-packaged samples) were opened, the laboratory room was immediately filled with the typical smell of decomposition. All samples already gave off a distinct putrefactive smell through the closed bags. The smell of coffee or similar odors could not be detected in any of the two samples – even when the bags with the wooden samples were opened and the odor was tested directly with the nose.
No chemical analysis were performed as this had neither been asked by the client nor had this been necessary for our investigation.
Ammonia
The rapid ammonia test as an indicator putrefactive liquid gave a clear result after just a few seconds of immersion; according to the manufacturer, this normally takes longer (Fig. 11).
Regarding the landlord’s statements
Corpse odor and “stains”
According to the client, “all employees... [of the landlord] who were in the apartment as well as the... [the landlord’s] crime scene cleaner and pest controller [...] stated that there was no corpse odor, only the smell of sanded wood.” This is not correct for the discolored wood: It smelled very distinctly of a decomposing corpse. Irrespective of this, there may have been a strong odor of sanded wood or another odor in the apartment. However, the odor of the corpse must have been perceptible in the immediate vicinity of the wood.
Flies
The clients state: “On his second visit to the apartment, the crime scene cleaner and pest controller took about 3 - 5 specimens of the flies from the large room to have them identified by a biologist friend. We were not informed of the results of the investigation.” The landlord is said to have stated: “An expert confirmed to us that these flies must have come from outside and could not have developed in the apartment.” This statement is partly correct: The insects may have flown into the apartment from outside because they were attracted by the corpse odor serving as an attractant for these insects. They do not necessarily have to have developed there. They can also “only” feed or lay eggs on putrefying tissue. The presence of the skin beetles and adult flies indicates that the colonization/ flying of insects into the apartment, which was either littered with animal meat or had a human corpse, had been taking place for some time: These are so-called late corpse colonizers. All of the insects we examined only occur at corpse sites with decomposing corpses or in environments with a high meat content in old waste (animal or human corpse parts).
DISCUSSION
The insects studied here are either corpse colonizers or are clearly associated with decomposition processes or animals attracted by them.
We are not aware of any odor that is similar in composition to the type of corpse odor present here. A similar odor can occasionally arise from mountains of garbage, which must then consist mainly of meat scraps. Only then does this odor develop, and then only after sufficiently long “maturing”. The time required for this depends on the temperature: The warmer, the faster. Since the apartment in the video sent to us does not appear to be full of garbage, but empty, there would have to have been a large quantity of garbage with a high meat content.
The ammonia test is triggered by the presence of decomposable substances, not by “normal” wood floors or pieces. This shows that decomposition fluid (and not coffee) must have penetrated the floorboards.
We have a video from the apartment which shows that there are cracks in the floor, including where the body is supposed to have been lying. Decomposition fluid and pieces of tissue from the corpse may have entered the area under the floorboards through these cracks (puddle of fluid). Cadaveric fluid can penetrate the actual wood of unsealed floors and then remain there or under the wooden floorboards owing to the adhesive properties of the semi-liquefied cadaveric material.
From time to time, these kinds of contaminated floors are sealed to “encapsulate” the odor or treated with chemicals to dissolve or mask the odor (for example with the raspberry odor of Maskomal or similar). However, it makes more sense to remove the source of the odor; this is comparable to used baby diapers, which are also thrown away or cleaned and not covered up in order to mask the odor.
The collective occurrence of the insects from the apartment samples certainly indicates the presence of at least decomposition fluid, the odor of which attracted the animals. The putrefactive liquid must have been in the wooden floor in sufficient quantity and presumably over a longer period of time, otherwise only blow flies would be found, which colonize corpses at an early stage. Skin beetles and chalcid wasps appear as later corpse colonizers [28]: Carpet beetles and their larvae use dried organic tissue and dead insects (such as flies) as a food source. However, they are less commonly found in apartments with corpses and piles of garbage, as the soiled areas are usually cleared and cleaned quickly. Chalcid wasps in particular are then naturally no longer attracted: They colonize the juvenile stages of other insects.
The absence of blow fly larvae and their pupae in the samples and on the photos indicate that there is now no fresh, new organic material available for the blow fly larvae to feed on. None was found anyway.
As blow fly larvae usually seek out dark and narrow “hiding places” to pupate, fly pupae and larvae could also be found under floorboards and behind carpet rails. This can occur from time to time and sometimes leads to strange occurrences of flies for the residents. For example, an apartment can be cleared and cleaned, but the pupae of the flies are still hidden in cracks and the flies hatch from the pupae later (see case 2 „Empty Apartment“ [29]).
The “mixture” of dead flies, beetles and chalcid wasps in the apartment concerned here means that the animals were attracted by the smell of corpses and died in the apartment or that there was sufficient food (including corpse fluid). It is irrelevant whether these flies developed in the apartment (from larvae) or whether adult insects have flown into the home. The main reason for their appearance is that they are attracted by the smell of decay.
Conflict of interest
The authors declare that they have no conflict of interest.
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