Forensic Entomology | Dr. Denise Gemmellaro
Questions from Lecture by Dr. Denise Gemmellaro
Ques : What is the acceptance of evidences in court of Law?
Ans : This depends on the court and where in the world you are. For example, in the US, there are two main standards for the admissibility of scientific evidence in course, the Daubert and the Frey Standards. But a lot of it depends on the Judge.
Ques : Is there any specific scratch pattern left on the bone surface once flies leaves the carcass, which can be used to identify at least genus of the fly , if not species?
Ans : Diptera larvae normally do not scratch the bone. Their mouthparts and the spines they have on their cuticle do not penetrate bones enough to create scratch marks.
Ques : How is it possible to recover a non-insect DNA from the pupa of an insect?
Ans : Non-insect extraction can be attempted using different primers, specific for the target species (for instance, human).
Ques : How can we calculate the age of blowfly after completion of one life cycle
Ans : Flies development depends on several variables, among which temperature. Generally speaking, the colder it is the slower their development, the warmer it is the faster their development. There are studies on the development of certain species of flies at different temperatures. These can be used as reference data in the estimation of the age of the collected entomological evidence.
Ques : Does rate of decomposition depend on the size of the body?
Ans : Yes, absolutely. The process and rate of decomposition depends on many variables; the size of the body is one of them.
Ques : How can DNA be extracted from Maggot found on a decomposed body?
Ans : Yes, it is possible to extract insect and non-insect DNA from the maggots feeding on a dead body.
Ques : Why DNA did not get damaged , contaminated or digested in the insects ?
Ans : It can. DNA is a molecule and as such it can deteriorate. Also, contamination is a possibility as well. Molecular analyses, however, can discriminate between insect and non-insect DNA. Moreover, if maggots are correctly and promptly collected, the chances of a successful extraction are much higher.
Ques : What is DNA barcoding ?
Ans : DNA barcoding is a molecular method to identify species using specific gene or genes. It is a method that does not rely on the morphology of the specimens, but on their DNA. Sequences of species are stored in databases to catalog different taxa and can be used as reference data.
Ques : Can we distinguish Ante - Mortem and Post - Mortem Injuries using entomology or insect patterns ?
Ans : It would really depend on the case. In some circumstances, we can see unusual colonization in certain parts of the body and that could indicate a wound inflicted on the body, or even a wound that could have potentially caused death. Insects though, while feeding on the body, will consume the tissues and therefore will cause damages to the body that can be confused with wounds. You will need the expertise of a pathologist and an entomologist to assess the nature of such damage.
Ques : Climatic conditions inhibit many insects and bacterias then how is the accuracy of PMI is affected ?
Ans : PMI and TOC (Time of Colonization) are estimates, and there are both expressed in the form of an interval. You can refine that interval using different reference data, considering variables (like climatic conditions) and of course doing research yourself to see what the actual effects of these variables is on the process of decomposition. In every report, all the conditions that could potentially skew the estimation of PMI or TOC should be listed.
Ques : Is there any distant learning mode through which we can get education or certification in Forensic Entomology. ?"
Ans : As of now there is no certification that can be obtained online. I am in the process of developing one, along with several other online initiatives. I can send you the information if interested.
Ques :How to become an entomologist?
Ans : There are several BS, MS and PhD program specialized in entomology. You could even do a BS in Biology, Environmental Science, Ecology/Evolution and then specialize later in Entomology with a graduate program.
Ques :What happens to the life cycle of any Blowfly, if the reason for the death is a poisonous lubricant?
Ans : I am not sure about the nature of the toxicant that you mentioned. In general depressant substances will slow down the life cycle and stimulants will accelerate it. When it comes to heavy metals they can accumulate in the maggots as well.
Ques :What is the decomposition period of semen in human body after dying
Ans : I would not know. It would really depend on all the variables mentioned before (temperature, humidity, quantity of semen) etc?
Ques : Does the decomposition time of the body by insect varies with climate change...?
Ans : Yes, insect activity is absolutely influenced by climatic conditions.
Ques : Does the insects are specific for particular crime scenes?
Ans : The species of insects that can be found at a crime scene depend on the geographic area. Also, different insects and arthropods can arrive at different moments of decomposition.
Ques : If DNA are found with the maggots, how are we extracting it from the insect body and how are we preserving. Doesn't the DNA degrade? If it does degrade what are the protocols to be followed?
Ans : If you promptly dissect the maggots and proceed with the extraction, there should be very good chances that the process is successful. You should not expose your sample to hot temperature and you should absolutely make sure the samples are processes as soon as possible.
Normally, maggots are killed in hot water and then placed in 75%-80% ethanol. In absence of ethanol, they can be frozen.
Ques : How we can collect and preservethe insects from the crime scene. Is there any other method of preservation if we want to extract DNA from the insect or we can follow the same procedure?
Ans : The same procedure discussed in the previous questions can be used.
Ques : What is the scope of forensic entomotoxicology?
Ans : Different substances can have an effect on insect activity and insect development. Entomotoxicology is the study of the identification and quantification of unknown substances using insects as substrates, the effects of such substances on their development and the potential forensic applications of these analyses.
Ques : Does clothes of a deceased affect the rate of decomposition? What if the dead body is completely covered? Then how insects are attracted towards it? And then how can we calculate the PMI in this condition?
Ans : Yes, clothing can have an effect on decomposition and insects activity on corpses. In general, any type of “barrier” between the insects and the body will delay insect colonization. Even if the body is dressed or covered, generally, insects will be able to find it and start colonization. For example, a body in a car, which is an “enclosed compartment” can eventually be colonized by insects; it would just take it longer for the insects to reach it.
Ques : What if a person died due to some poisoning? Can we extract poisons from insect?
Ans : Theoretically, it is possible if the analysis is done on the gut content of the insects.
Ques : What is the suitable way for collection the pupa or larvae from the crime scene to the lab.?
Ans : Larvae should be collected with a plastic spoon from all body regions where they are observed. Every sample should be split in half: half of it should be immediately killed in hot water and preserved in 75-80% ethanol and half of it should be placed in haired containers with some food (the standard is beef liver), a pupation substrate (saw dust or vermiculite). The containers should be brought to the lab and the maggots should be reared to adulthood under controlled conditions.
Pupae should be placed in an aired container with no food and brought to the lab where they will be kept under controlled conditions until eclosion.
Overcrowding should be avoided both for maggots and pupae.
Ques : Does each environment have its own insects?(dessert/ forest/rocky area)
Ans : Generally speaking every ecoregion has a specific entomofauna, but there can be overlapping among areas.
Ques : Do insect activities can be seen in burnt body cases too?
Ans : Yes, absolutely. In my personal experiments, burned carcasses are consumed by insects more quickly than non-burned ones.
Ques : If death occur due to intoxication of any drug will that have impact on insect activity like will it increase or decrease the time of decay? "
Ans : It depends on the substance. Generally speaking, depressant (heroin, alcohol etc.) will slow down the life cycle of flies and stimulants (cocaine, methamphetamines etc.) will accelerate it.
Ques : Can any drug or toxic substances be harmful for insects too?
Ans : Yes, it can. But it depends on the type of substance and on its quantity.
Ques : What's the role of maggots in case related to drowning?
Ans : When bodies are thrown in water, unless rare circumstances, they will go through a stage that will make them float on the surface of the water. When they float, one part of them will be exposed to terrestrial insects, meaning also flies, which can lay eggs on them. Therefore, maggots can be observed and used forensically, as they would traditionally be.
Ques : How many life cycles does an arthropod would be able to complete on an adult human dead body? in control and natural environmental condition.
Ans : It depends on how much tissue there is and how fast it dries up. Once the soft tissues have been consumed by maggots and once the tissue it too dry, adult flies will no longer be attracted to that body, because it would no longer be suitable to lay eggs (the new maggots would have nothing to eat!).
Ques : If maggots consumed human flesh and convert into pupa and further into fly, is it possible to extract human DNA from adult fly?
Ans : Non-human DNA has been successfully extracted from immature (maggots and pupae) blow flies and from empty puparia. I am not sure if human DNA coming from the food substrate of maggots has been extracted from adults. I know that they can be exposed to human DNA and that such DNA can be transferred by them.
Ques : During the research on pig carcass to estimate the temperature, if one can put a sensor rod inside it and connect it with a recording unit having real time interval of 1 minute. Is it possible to understand the effect of temperature difference between environment and inside carcass on the growth of maggots? "
Ans : Having a constant monitoring of the internal temperature of a carcass would surely help the estimation of time of colonization. It is surely more accurate than obtaining the temperature from the closest weather station.
Ques : Regarding the collection of maggot , we have to send both live and dead maggots to the laboratory or only live maggots and how we will differentiate species by seeing maggots?Can you elaborate the collection of maggots and other stages ?
Ans : Both. Dead maggots are useful to “freeze” the crime scene. It is like taking a picture of the crime scene. And also, in some cases, the species of blow fly can be identified using maggots. The live ones are important because rearing them to adulthood under controlled conditions allows for an easier identification and helps the estimation of Time of Colonization or TOC.
As for the collection process:
“Larvae should be collected with a plastic spoon from all body regions where they are observed. Every sample should be split in half: half of it should be immediately killed in hot water and preserved in 75-80% ethanol and half of it should be placed in haired containers with some food (the standard is beef liver), a pupation substrate (saw dust or vermiculite). The containers should be brought to the lab and the maggots should be reared to adulthood under controlled conditions.
Pupae should be placed in an aired container with no food and brought to the lab where they will be kept under controlled conditions until eclosion.
Overcrowding should be avoided both for maggots and pupae.”
Ques : Do blow flys or other flys prey on burned bodies and if yes can we identified the chemical substance like petrol or other substance used in burning from flys.
Ans : Yes, theoretically, fuels, accelerants and other substances could be isolated from the gut content of maggots.
Ques : If any toxic substance present in dead body...so is that harmful for insects?
Ans : It could be. It depend on the substance and its quantity.
Ques : How can the perspective of entomotoxicology be applied on maggots and diatoms?
Ans : I am not sure about diatoms, but maggots can be used as a substrate to extract toxic substances and can therefore contribute to the forensic investigation.
Ques : Is that how the climatic changes effect on the maggots and if then how can the PMI be estimated?
Ans : Climatic changes are making blow flies (and other taxa) change or expand their range. Therefore, it is useful to conduct surveys of geographical areas to know which species are there and use those data in the event of a criminal case containing entomological evidence.
Ques : How can one recover the DNA from the flies, feeding on the dead body.
Ans : You can dissect the maggots feeding on the body and conduct an extraction on the gut content of those maggots.
Ques : Does finding antemortem or postmortem drowning on the basis of location of presence of diatoms in the body also included in forensic entomology? If yes than what is the method for this analysis?
Ans : Yes, some forensic entomologists also have experience with diatoms. Normally, the presence of diatoms in the lungs of a corpse found in water can be a sign that that person “breathed” water (containing diatoms) and it would explain the presence of those diatoms in the lungs. This could be an indication of the cause of death. Moreover, since a body of water can have specific diatoms, the analysis of diatoms can help identify the place where the drowning took place.
Ques : How many different kind of insects feed on the human dead bodies? Is there any relation between different insects feeding on different kinds of tissues or organs?
Ans : The two main insect Orders associated with decomposing remains are Diptera (Flies) and Coleoptera (Beetles). Within this orders, there are numerous families that have been observed on decomposing matter. Calliphoridae is probably one of the most common taxon associated with dead bodies and one of the first to colonize dead bodies.
Different stages of decomposition have been associated to different groups of insects, sometimes defined as “waves” of insects; this is an ecological concept known as succession. On the basis of succession, analyzing the types of insects observed on a carcass can help estimating the stage of decoposition the body is in, and therefore can help estimate time of death or time of colonization.
Ques : What about the scope in forensics entamology in india
Ans : It is the same as in any other part of the world. The application of the study of insects to criminal legal investigations, to stored product investigations and to urban entomology investigations.
Ques : Do flies attracted to lay eggs on burnt corpses? Thank you.
Ans : Yes, flies are attracted to burned bodies and will lay eggs on them!
Ques : How long it takes to investigate by entomologist a person who is murdered by someone
Ans : Entomologists investigate the entomological evidence, not the body. The body is just a substrate for the insects, but the main interest for a forensic entomologist should be the entomological evidence. As far as time, it depends. Sometimes the analysis can take one or two weeks, other time it can take months. It depends on the evidence that is collected, on how well that evidence is preserved, on whether or not molecular analyses are necessary and on many other variables.
Ques : Apart from toxic chemicals which are different factors those affect life cycle of fly?
Ans : Temperature, humidity, photoperiod, type of food, climatic conditions, bacteria, fungi, oxygen content and probably other things that I can’t think of right now
Ques : How the DNA analysis of non-insects is being conducted in pupae?
Ans : Same way as in other substrates. It is important to use the proper primers and to conduct the analysis promptly for best results.
Ques : I would like to know more about the effect of drugs, such as that of cocaine (as shared by Dr. Gemmellaro), on the insects when they ingest it via dead body.
Ans : It will depend on the type of drugs. As said before depressants would slow down development and stimulants would accelerate. There are a few papers on the effect of different types of drugs on the development of blow flies. However, more research is needed in this field. There are a lot of ethical and practical problems associated with entomotoxicology research, but steps are being made in the right direction.
Ques : What causes mummification of a dead body at extreme high temperatures?
Ans : Along with temperature, ventilation is needed for mummification to happen.
Ques : Do maggots eat hair also? Or the hair are decomposed?"
Ans : No, maggots eat soft tissues. Hair and other keratinous substrates (like nails) can be decomposed by certain beetles families that arrive in the later stages of decomposition, like Dermestidae (carpet beetles).
Ques : If a person is drug addict, does it affect the rate or process of decomposition, also does it affect the time of appearance or presence of some insects on the body?"
Ans : It can affect both. It really depends on the substance this person is addicted to and on the effects the addition has already had on the person (weight loss for instance).
Ques : How DNA can be found from insect , will it not be digested
Ans : If extracted promptly, there are good chances to recover ingested DNA.
Ques : Climatic conditions inhibit insects pattern for a while then how much accurately can we determine PMI.
Ans : All biotic and abiotic factors will have an effect on the estimation of PMI and TOC. It is important to use the data that one has available and account for all the other variables that are observed on the scene. One can make an estimation using the reference databases that are available and then can say, in the report, that there are other factors that make have an effect on the calculated estimation.
Ques : Is it possible to diifertiste Am wounds from pm from insect activities?"
Ans : You would need the help of a pathologist. See the previous question regarding wounds.
Ques : How much data is correct of Entomologist for murder investigation.
Ans : I am not sure what this question means. Entomologists can contribute valuable information in murder investigations in the entomological evidence is properly collected and analyzed. I hope this helps.
Ques : What determines decomposition
Ans : A lot of factors! Body mass, fat percentage, clothing, temperature, humidity, weather, insects, indoor vs outdoor and so much more!
Ques : Does the life cycle of one insect hampered due to presence of any other insect feeding on the dead body?
Ans : Different insect taxa can influence each other. Some species are predators and will therefore arrive later on a body and consume the insects that are already there. Other insects will arrive on the body attracted by the pheromones released by insects that are already feeding on it. There is a lot of interactions among necrophagous and necrophilous insects and many of those are studied by decomposition ecologists, in addition to forensic entomologists.
Ques : What are the different environmental conditions that effect estimation of PMI with entomological evidence?
Ans : All environmental conditions can have an effect on entomological activity and therefore on the estimation of PMI or TOC.
Ques : Can you please furnish information on certificate program in forensic entomology
Ans : As of now, it is possible to obtain a certification as forensic entomology technician through the American Board of Forensic Entomology (ABFE). Information can be found on the board’s website https://forensicentomologist.org
Ques : Which are the methods for species identification?
Ans : To identify species it is possible to use morphological features of the specimens. This requires the use of dichotomous keys that may or may not be present in all geographical areas and for all species.
In addition to morphology, DNA can be used for species identification. This method is known as barcoding and consists in the analysis of specific genes that allow for the identification of one taxon without using morphology.
Ques : Can you elaborate on topic PMI calculation, like u said in one of the case PMI was calculated as 6 yrs. So if u can tell us the series of events which lead to determination of TSD as 6 yrs. And I also need a little clarification on how to calculate no. Of cycles insect has completed over dead body assuming it's more than 5 or 6 cycles.
Ans : In the example I gave, PMI had been estimated as 6 years using the seasonality of the dead insects and insect remains that were found around the body. For example certain beetles exuviae recovered near the body are spring species have a life cycle that lasts about 2 years. Combining all this information for all the taxa, it is possible to arrive to the general estimate of 6 years.
In regard to the number of cycles completed on a body, I am not sure that it is wise to assume that more than 5 or 6 cycles are completed. It largely depends on the size of the body and on the rate of decomposition of the body. More studies are surely needed to explore this topic, but some have been performed. For instance, a study was able to discriminate between “old flies” and newly eclosed flies by looking at the damages on their wings.
Ques : Is it possible to have insects if the cadaver is inside the freezer?
Ans : No. If a body is in a working freezer, insects should not have access to it. It is the reason while we can safely store food in our freezer without worring about insects.
Ques : Can the identification of specific types of drugs be done from the blowflies or insect found on the victim if he has consumed them before death ? If yes ,from larvae also ? And for how much time can it be still identified?
Ans : Yes, those analyses can be performed using the gut content of maggots as substrate.
Ques : Can fingerprints be developed from decomposition state of body? If yes, then how?
Ans : In some cases, if the body is not heavily decomposed, fingerprints can be acquired from a corpse.
Ques : Is it possible to determine whether the death was due to some grave injuries (not affecting the bones) even after the body is skeletonized, from entomological evidence?
Ans : Once all the soft tissue is gone and only bones remain, injuries can be assessed only if they affected I bones.
Ques : In sexual assault cases ..can we get desired amount of DNA of suspect from insects colonising in pubic region of victim, if the DNA itself is in very small amount..? If yes then how much sample we will have to collect so as to get the good amount of suspect's DNA..?
Ans : Yes, obtaining DNA from an unknown suspect in cases of sexual assault is theoretically possible if the suspect left some genetic material (semen) on the body. If extraction is done using gut content from maggots, I would use probably several maggots, to increase the chances of a successful extractions. I would not know about the specific number because it would depend on how many maggots are there to begin with.
Ques : In the above case for how many days after death the DNA can be desirably extracted from insects without getting destroyed..?"
Ans : If possible, I would not wait for more than one day to proceed with DNA extraction.
Ques : How do we extract DNA from Maggots when they ingest Human DNA? How do we differentiate between the two genetic matierals i.e. the human DNA and the maggot DNA?
Ans : It is possible to use different primers to target specific DNA material, insect DNA, human DNA and so on.
Ques : Is it really possible for a maggot or any other life stage of an insect to stay inside mouth or any other part of a living body? if yes then what will be the time period of their survival inside the living body? and what could be the favourable and unfavourable conditions for any maggot to stay alive inside the living body?
Ans : They can. The process of myiasis is indeed the colonization of a living host by insects. If undisturbed, they can stay inside their host even for weeks, until their development is complete; while inside their horst, they will keep eating (the host) and breathing.
Ques : What if any environmental factor disrupt the life cycle of insect?
Ans : All environmental factors can have an effect on the life cycle of insects. See previous questions for more details.
Ques : In case the entire body is eaten up by the insects, then how such case can be studied?
Ans : If the insects are still there, insect development can be used to estimate tome of death and time of colonization.