Foresics Unit biotechnology

What is forensic science- use of science to investigate crime and present unbiased scientific evidence in court. They draw knowledge from chem, bio, and physics. They assist authorities by techniques to analyze evidence in the laboratory

Part 1: forensics and the law 

• If you don't analyze it following the law or talk about it using the law then you can’t use it in court 

• Every pass of evidence that is passed by you will be in court 

Who is present at a crime scene during the initial investigation:

• Forensic analysts - do testing like is it blood, what happened here, and sends it to the lab 

• Police 

• Paramedics  

Crime scene investigator/analyze 

• Not a forensic scientists 

• They need to be reported at any time 

• Hours are terrible, work conditions are terrible 

• Don't really have that much time 

Forensic scientists

• Analyze the physical evidence using scientific practices 

• Need a BS in lab based science 

• Lab research experience 

• MS in lab-based science or forensic sciences 

• Internships in FS lab 

• Bachelors or masters 

• They work in the lab and medical examiner’s office 

Chain of custody- from the time evidence is 1st encountered until til appears in court, someone must maintain secure accountable possession of it. 

(collection, examination, analysis, reporting) 

(media, data, information, evidence) 

Forensic Scientists don't collect evidence. But they need to be concerned about the chain of custody, why?

• The defense can say the evidence was tampered with if the chain of custody is broken 

• You can have all the work but then it cant be used if chain is broken 

Evidence analysis and prep for court may take many months 

• Without proper handling of evidence, judge can make it inadmissible in court IMPOSSIBLE 

• Time and effort goes to waste 

Why do Forensic scientists have to testify in court?

• Have to be good at talking about what they do 

• U gotta be good at science 

Scientific Evidence(Court 

What is scientific evidence???

• Most often presented in court by an expert witness testifying on expert opinions

• Included expert testimony 

• Expert is called to interpret results and draw conclusions 

Rules of evidence

Frye Standard

• You may use methods and approaches that has to accepted by the scientific community 

• Such as using a microscope or blood typing  

• Not fingerprints or dna analysis 

What is Daubert v Dow Pharmaceuticals?

• Case where someone was trying to hold the pharmaceutical company for a drug that affected someone really badly but it set the standard that scientific evidence may be admissible if it had been used for scientific research in the past and is a valid method for that purpose. 

• Need an expert witness 

The Daubert standard often leads to a battle of the experts, what this mean?

• Turns the jury off and you don't want this 

• The jury is listening to 2 people at the same time about scientific stuff

• When both sides have opposite views about some scientific technology, they call experts to argue with either side. 

Freye v Daubert

• frye : generally accepted by the scientific community 

• Daubert: the testimony is based upon sufficient facts of data, the testimony is the product of reliable principles and methods and the witness has applied the principles and methods reliably to the facts of the case. 

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Part 2- analyzing the evidence 

2 types of forensic analysis that forensic scientists do:

1. Identification- what it is 

2. Comparison- what is it the same as/similar to 

Exemplar- items of a known source and identify used for comparison(control) like collecting shoes to compare to footprints at the crime scene 

What information can physical evidence provide?

Type of crime and level

1. Premeditated murder with intent to kill (first degree)

2. Not planned murder(2nd degree)

3. Man-Slaughter- someone dies by your actions but you didn't intend for them to die  voluntary(you did something and you knew) and involuntary(self-defense) (3rd degree) 

Analysis of Physical Evidence- 

• Determine the actions at the scene 

• Confirm verbal testimony 

• Identify the victim or Who was there( person of interest)

• Provides leads to detectives 

• Validate or refute a claim 

• Rule out individuals usually not ruling people in. Classifying types of evidence 

Class evidence: links to a group and has unique characteristics that links to a specific object but not a specific individual like shoe prints.

Individual evidence: high probability that the evidence from a specific individual 

Identify evidence(ident): A type of individual evidence that links to a specific individual as the source like DNA, skin, poop

Types of physical evidence:

• Body FLuids can tell you if drugs were involved or toxicity 

• Documents 

• Drugs 

• Explosives 

• FIbers 

• Fingerprints 

• Firearms/ammunition 

Ponderous of evidence - level that is needed of evidence to convict someone for a civil case .  linking physical evidence by ruling people out. 

Comparing types of evidence:

Individual characteristics

• Evidence associated to a unique source, blood DNA

Class

• Evidence associated only with a common source like hair, footprint, blood for blood type

Divisions of the lab 

1. Biologist: DNA and Blood evidence who also works with bodily fluids like is it blood, what type of blood, can you get DNA from it, and the spatter pattern of the blood. 

2. Forensic chemist that identifies drugs and unknown substances found at a crime scene like Meth, Crack, Cocaine, Mariwana. They know which gangs can be associated and who is probably involved  

3. Trace Evidence Analyst- identify and compare small pieces of physical evidence and often the “forgotten evidence”’(small evidence like hair and fibers) or excelerents some common ones are: automobile accidents or paint chips) they  use mass spectrometry  

4. Document examiner who examines handwriting analysis, forgeries, fake documents, and counterfeit money (lottery tickets are commonly forged). 

They use different types of light and magnifying lens, chemical analyst

5. Firearms, toolmarks, and impressions- they identify guns, link bullets to specific guns, determine source of prints, marks, and causes of damage from tools. 

6. Ballistics and Tool Marks & impressions examiner are in the same division as fire marks

Forensic Toxicologist- analyze fluid and tissue for signs of position, drugs, or other substances, can work with living or dead, often in medical examiner’s office 

Specialists - employed in another field, called in for special cases, provide expert testimony in court such as:

Forensic Odontologist- dentists that come in for pieces and parts and come usually during plane crashes or bombs 

Forensic Entomologist- look at insects 

Forensic Anthropologist- bones can tell you age, gender, cause of death

Forensic Psychologist- PHD in psychology and work with criminals and counsel people can develop criminal file 

Making the case:

1. Reasonable suspicion, probable case, preponderance of the evidence, proof beyond a reasonable doubt 

2. Look at trifecta of investigation like the Means, motive(hardest to prove), opportunity 

Blood notes:

• Plasma: protein, water, solute

• Red blood cells are around the size of a yeast

• Hemoglobin gives the blood its color 

• Blood: orange/brown 

• Richer red blood cells: lack a nucleus and have no DNA 

• Glycoproteins: antigens 

• Hematocrit: ratio of red blood cells to plasma 

• Formed elements: red and white blood cells 

Forensics:

• Injury can cause blood loss 

• For a healthy adult: 20% loss of blood volume(1L) first system is restlessness 

• Then at 40%, hypovolemic shock sets in 

• Blood pressure- regulates blood volume and movement 

• Blood pressure- regulates blood volume and movement 

• Tissue perfusion(bruise) blood reaches tissue 

• Organs and tissues- need constant supply of blood, especially the brain 

• Brain- number 1 place that needs blood 

• Bruising- burst capillary beds under the skin cells 

Alleles: letter representing genotype (I^A) (I^o)

Genotype: gene forms/types like homozygous recessive, heterogeneous dominant  

Phenotype: the words 

Luminol: good for trying to clean up 

Cross linking: causes agglutination 

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Chromatography - separation method (paper, gass, then layer)(purpose: separate compounds in a mixture)

• Separates a mixture into discrete components 

• Separation is based on chemical properties 

• Polarity differences or similarities are the key properties of this separation

PCR NOTES

What is PCR: 

Applications of PCR:

• Cancer research, fingerprinting, drug discovery, etc

natural obtained DNA is typically not concentrated enough for molecular analysis 

Amplicon- you will have 2 different ones from mom and dad, but if the mom and dad is the same then you will have 1 amplicon. 

Portion of DNA replicated during PCR, observable as a band in gel electrophoresis, requires primers to mark the start and end of the region being copied(amplified) 

When making the primers you want to think about the organism because different organisms have different lengths of its genes based on how much you want to amplify you need to look at the primers 

PCR- put gel towards negative end of electrophoresis box so it can run to red(positive)
Loading dye- colors sample and weighs the sample down in the buffer

What is true about STRs? 

• STR’s smaller pieces of DNA can be easily amplified by PCR 

• THey are less likely to degrade since they are small

• Can be use with a tiny drop of evidence 

Genome- complete set of genetic information that an organism carries in its DNA 

PCR- technique that uses cycles of temperature changes to copy DNA sequences, amplifies a DNA sample. 

Order: denaturation of double strand(over 90 degrees), binding primers(annealing when temperature cools), building double strand(extension)

Helicase is not apart of the actually PCR reaction 

Taq Polymerase is used in PCR because the Human Polymerase would denature 

Forensic Entomology- use of insects that feed on remains to help investigations dr

Medical examiner and forensic pathologist is the same person 

Frye v. United States was the case to let scientific evidence be used in court 

Physical evidence is any substance or artifact that tends to establish or disprove a fact 

Replication form is when the helicases break the hydrogen bonds

The lagging strand of DNA is copied discontinuously and moves away from the replication fork 

Okazaki fragments at the fragments that grow on the lagging strand 5’ to3’

Eukaryotes package DNA with histone proteins 

There are 5 carbons in the sugar in DNA 

The 5 prime carbon in DNA is not a part of the carbon ring structure 

The phosphodiester bonds in the backbone of DNA have  negative charge 

Pyrimidine bases are single rings and purine bases are double rings 

Class evidence- a link between a type of item and a group of people who have them 

The biology branch of forensic science identifies body fluids 

TLC- presumptive test 

Stationary phase - silica on a glass plate 

Mobile phase- of TLC is the solvent 

The plate in TLC should be place upright and samples added on the non-shiny side 1 cm from bottom of plate