Forensic Entomology Quiz 3

ADD

Degree days are added to reflect periods of development this is called

Thermal units

Describes the environmental energy insects use for growth.

• Red gut indicates there is food in digestive track • Will decrease in size before pupating

How are the age of maggots prior to migration estimated?

instar

How are the age of maggots prior to molt determined?

Algor Mortis

- Cooling of the body - Follows log curve but use linear estimation - Time scale 18-30 hours - 1.5 degrees per minute cooling o Did individual have elevated body temp at the time of death? o Drugs, high metabolic rate

Rigor Mortis

- Stiffening of muscles - Starts in face and progresses down o 2-6 hours begins o 12 hours fully developed o 2-4 days - gone

Livor mortis

- pooling of blood 1 hour=noticable 3-4 hours=fully developed 12 hours= fixed

ADD = Time (days) * (ave. temp - baseline temp)

ADD equation

ADH = Time (hours) * (ave. temp - baseline temp)

ADH equation

• Darker=older

How are the age of maggots estimated by pupae coloration?

• recently oviposited or ready to hatch? • Unhatched are sticky and more yellow Hatched are dry and whiter

How are fly eggs age esimated?

-Maggots can be used as soft tissues when they are absent in corpses. -They can show drugs and toxins via chromatography. -Stimulates such as cocaine can cause maggots to eat faster thus developing at a faster rate. -Some toxins like mercury can slow down the decomposition rate of a corpse.

How are maggots used in toxicology? How can drugs and other toxins affect decomposition rates?

-Any drug can show deviations in normal development patterns. -Drug toxins are locked in the cuticle indicating they will be preserved long after the body is decomposed. -Hide beetles do not show indication of drugs as much because they feed on dried skin. empty pupal cases can lock in these drugs for years.

How do can evidence of drugs linger in crime scenes years after the body is gone?

-Social insects can affect the PMI -Some wasps eat maggots and other necropharous species. This can extend the normal period for flies laying on the carcass. -There was also a wasp nest found in a girl's skull. This helped determine time of death because the sections were empty, and they determined what time of year these wasps lay eggs.

How do social insects effect the decomposition of a body?

- Different coverings make for different PMI calculations. If the body is concealed in a thick covering then the decomposition rate will be much lower than that of a loosely wrapped body. - The coverings also can account for lack of predators considering the maggots cannot escape into the surrounding soil

How do tight and thorough coverings compare to loose coverings of a body?

-Burned carcasses prove extra attractive to flies. The cracked skin from the fire made burned carcass have insects 1 day before the control. -Burned specimen of wet habitats decomposed even faster than dry. Egg laying occurred 4 days before and lasted longer.

How does burning a body affect decomposition rates?

-The body will dry faster when exposed to the air and only things with wings could get to it before it touched the ground. -There is a drip zone where everything falls. Maggots on the outside of the Maggot ferris wheel will fall to the ground -Dermestids only got to the corpse when the feet touched the ground.

How does exposure to the air affect decomposition? LIke if a body is hung in the air

-Salt water can affect when insects arrive on a body. Salt water itself slows down hatching. -if a dead man was on a boat it would take several days for bacteria to make him smell bad enogh for flies to venture a mile out from shore.

How does the ocean affect decomposition?

18-30 hours after death

How long is algor mortis good for?

not good after 12 hours of death

How long is livor mortis good for?

not useful if body is out of rigor for 48-96 hours after death

How long is rigor mortis good for?

Warm and not stiff Warm and stiff Cold and stiff Cold and not stiff

How was the time of death detected in the 19th century?

poikilothermic

Insects are _____________________ meaning they must use the environment as a source of heat

1. Find the published literature that gives the developmental time for each life stage at a temperature that is closest to the average daily temperature of the crime scene. There may be more than one paper for your species of interest, be sure you have justification as to why the paper you used was a better choice than the other(s) 2. Find the published literature that gives the baseline temperature for the species of interest. 3. Use the ADD/ADH equation to calculate ADD/ADH using the data from the published literature (Steps 1 and 2)!!!! 4. Find the nearest weather station to the death scene to obtain the average daily temperatures for a period of time before and after discovery of the body. Be sure you know the distance from weather station to the death scene. 5. Get the average daily temperatures from the ibutton that was placed on day of discovery and collected at least 5 days later. 6. Graph your data to get a trend line. 7. Use trend line to determine the average daily temperatures at the crime scene prior to the discovery of the body (correction factor). 8. Set up an excel sheet to calculate ADD/ADH for the crime scene (more to follow on how to do this)

Steps to calculate PMI for a particular species of interest

1. homicides occur at night 2. Flies begin to oviposit as soon as they discover the corpse 3. Faunal succession is predictable 4. Weather conditions at the site distant from the death scene reflect conditions at the scene 5. Ambient air temperatures are a major factors influencing the rate of development

What are some common assumptions when calculating PMI using insects?

-Carrion is in a stable environment where weather data is fairly constant. -Maggot lengths and weights increase over time until a certain point

What are the assumptions for Growth Curves?

- individual species characteristics -weather and seasonality -presence of maggot masses - food type - presence of drugs and toxins -geographic region

What can influence development and succession?

1. Amitriptyline 2. Ethanol 3. Meth Metabolites (Ecstasy) 4. Morphine

What drugs decrease the speed of larval development?

1. Heroine 2. Methamphetamines 3. Phencyclidine 4. Cocaine 5. Diazepam

What drugs increase the speed of larval development?

1. • Correct species identification! 2. • Base temperature for each species of interest 3. • Temperature data from the crime scene (not always available) 4. • Weather station meteorological data that is closest to the crime scene 5. • Correction Factor 6. • Species developmental data for each life stage

What is needed to calculate ADD/ADH?

Myiasis

When live human tissue is infected with maggots

Can be used for longer amounts of time after death and can still be used when soft tissue is gone

Why use forensic entomology instead of rigor mortis, algor mortis, and liver mortis?

- blowflies are the first witnesses - succession rates can be calcualted

Why use insects for PMI?