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DETERMINING THE MANNER AND TIME SINCE DEATH

Unit 2

How do police estimate how long a person has been dead WHEN THEY ARRIVE ON SCENE?

• Temperature of the body

• Stiffness of the body

• Responsible for examining a corpse in order to determine cause of death

• Record temp of body, temp at scene of crime, weight of victim, etc.

Forensic pathologist

Livor mortis• Setting of blood in the lower portion of the body that causes a

purplish red discoloration of the skin

RIGOR MORTIS

• Chemical change in muscles after death that causes the limbs to become stiff

• Caused by a halt in ATP action

THE EYESEyes develop a thin cloudy film 3 hours after death.

Eyes also become softer due to loss of fluid pressure behind them

SKIN COLOR

• 48 hours after death, bacteria starts to grow on skin giving it a greenish color.

• Starts in lower stomach area and spreads outwards

ALGOR MORTIS

Steady decline in body temperature until the body reaches ambient temperature. As body starts to decompose, the temp rises again.

Fun math part!!!• Estimated body temperature drops at a rate of 0.8K per hour

• To convert kelvin to Celsius, subtract 273.15 from the kelvin temperature.

• Example: A person’s normal body temperature is 310K, convert that to °C.

•• 310K• - 273.15

• ----------------• =37 °C

• To convert Kelvin to Fahrenheit:

1. Multiply the kelvin temp. by 9/5

2. Subtract 460 from the above number

• THIS YIELDS THE TEMPERATURE IN °F

•Convert 345.5 K to °F

• 345.5 x 9/5= 621

• 621• -460

• _________• = 161 °F

• °F to °C Deduct 32, then multiply by 5, then divide by 9

• °C to °F Multiply by 9, then divide by 5, then add 32

• First it’s important to know that human body temperature is 98.6 °F

• Then you can convert from there

• 98.6°F• -32• ______• =66.6• x 5• ________• 333• /9

• =37°C•

What’s human body temperature in °C?

SO WHY IS ALL THIS IMPORTANT?!?!• Going back to what we said earlier, if we know a person’s body

temperature drops at a rate of 0.8K per hour after death, what would be the temperature of a person that has been dead for 3 days?

• *NEGLECTING EXTERNAL FACTORS*

• 1 day= 24 hours• 3days= 72 hours

• 72hours x 0.8K = 57.6K temp. drop

• So if you know normal body temp is 98.6 °F• = 310 K• 310k- 57.6 K = 252.4 K

• 252.4 K= -5.68 °F• BODY GETS REALLY COLD REALLY FAST!!!

IMPORTANT TO NOTE!

• The body would never actually get that cold.

• It actually only cools down until it gets to ambient temperature.

• Chemical processes involved with decomposition cause the body to warm back up.