Chapter 8 Blood and Blood Spatter

Transcription

1 Frensic Science Student Ntes Chapter 8 Bld and Bld Spatter Name Class ( P / W ) Objectives By the end f this chapter yu will be able t: Explain: the cmpsitin f bld Describe: Determine: Chapter 8 Bld and Bld Spatter Calculate: the prbability f certain bld types Cnduct: Examine wunds and describe the nature f the weapn Find and prcess bld evidence Intrductin Bld as evidence Bld can be typed Types: Bld type can prvide: Why? White bld cells cntain. DNA prfiling can prvide: Why? N tw peple have the same DNA (except fr identical twins) Histry (See page 196 in text) Our understanding f bld began in ancient times and cntinues t grw tday. What was the first nted use f bld? Wh nted that bld circulates cntinually thrughut the bdy? In what year? What item f significance was discvered in 1901?

2 Frensic Science Student Ntes - Chapter 8 Bld and Bld Spatter What (nte when) discveries were made related t bld dnatins/transfusin? What (nte when) discveries were made related t using bld in frensics? Explain hw it is related. Cmpsitin f Bld Whle bld is cmpsed f: the fluid with hrmnes, cltting factrs, and nutrients. Red bld cells carry t the bdy s cells and away. Cntain Hemglbin Platelets Cntains Binds t Gives red bld its Aid in and the f damaged bld vessels. Bld Typing Bld typing is and than DNA prfiling. Page 2

3 Frensic Science Student Ntes - Chapter 8 Bld and Bld Spatter 1900 Karl Landsteiner discvered that when bld frm different peple was mixed, it smetimes caused. A persn s bld type is determined by the presence r absence f fund embedded in the cell r plasma membrane f red bld cells. Bld Types: Presence r absence f and prteins determine letter f type These are cell surface prteins Percentage f US ppulatin with each bld type Presence r absence f Rh prteins determine psitive r negative f type Discvered by Alexander Weiner in mnkeys in 1940 (+) (- ) Antigens are If yur bld type is A and yu receive A bld, will yur bdy see the A prtein n that bld as freign? Why r why nt? If yur bld type is AB and yu receive B bld, will yur bdy see the A prtein n that bld as freign? Why r why nt? What bld types culd AB recipients receive withut having antigens? Page 3

4 Frensic Science Student Ntes - Chapter 8 Bld and Bld Spatter What bld types culd O recipients receive withut having antigens? Antibdies are Antigen- Antibdy Respnse Agglutinatin - Clumping Respnse One arm f the Y- shaped antibdies attaches t Remember - The antigens are the A/B/+ prteins frm the dnated bld that are freign t the recipient bdy/bld. The ther arm f the Y- shaped antibdies attaches t This results in Additinal Prteins and Enzymes There are many additinal enzymes and prteins fund in the bld that are imprtant fr identificatin purpses. MN PGM AK ADA Calculating Bld Typing Prbability Given the frequency f different genes within a ppulatin, it is pssible t determine the prbability that a particular bld type will appear in a particular ppulatin. T determine the prbability f tw separate events, it is necessary t Page 4

5 Frensic Science Student Ntes - Chapter 8 Bld and Bld Spatter Examples What is the prbability f thrwing tw dice and getting tw sixes? What percentage f the ppulatin wuld have A+ bld? By identifying the additinal prteins in the bld evidence sample, investigatrs can limit the size f a suspect ppulatin and help identify a suspect. What percentage f the ppulatin wuld have O-, MN bld types? Bld Spatter Pattern In 1939 the meaning f the spatter pattern was first analyzed. In 1955, bld spatter was Used tday t When a wund is inflicted, It takes a gruping f t make a bld spatter pattern. The pattern can help t Page 5

6 Frensic Science Student Ntes - Chapter 8 Bld and Bld Spatter The pattern can indicate: Bld Spatter Science Gravity pulls bld tward the Air drag prvides t the drpping bld Chesin causes the mlecules t stick t Bld maintains a When bld drps t the grund, it will maintain a curved surface (chesin) Newtn s Third Law: Frce = = If there is enugh frce when the bld hits the surface, the chesive bnds can be brken and bld will frm satellites Enugh Enugh When it falls nt a less- than- smth surface Bld Spatter Patterns Page 6

7 Frensic Science Student Ntes - Chapter 8 Bld and Bld Spatter Patterns can help investigatrs determine the type f weapn used. What kind f a pattern is prduced by a gun sht? What kind f a pattern is prduced by a hammer blw? Bld Spatter Pattern Angle f Impact Calculate with tw measurements Impact Angle θ = sin - 1 (width/length) Stain is mre elngated with faster mvement Slwer Faster The shape f an individual drp f bld prvides clues t the directin frm where the bld riginated. Tail shws directin Hw will the pint f impact cmpare with the rest f a bld pattern? Page 7

8 Frensic Science Student Ntes - Chapter 8 Bld and Bld Spatter Bld Spatter Pattern Lines f Cnvergence Draw straight lines dwn the axis f the bld spatters. Where the lines cnverge, the bld riginated. Bld: Crime Scene Investigatin 1. Search fr bld evidence. 2. If any is discvered, prcess it determining: 3. Interpret the findings: Bld Spatter 101 Page 8