Screening and Serology PPT

Question 1

Screening is the ______ and _______ of evidence for DNA analysis and or preservation

Answer 1

Examining and sampling

Question 2

What are three ways evidence is evaluated before examining?

Answer 2

Ensure that the Sub form/ portal receipt is consistent with the evidence packaging and that it is consistent with the DNA Unit Evidence Submission Policy
Determine the Forensic question
Checking communications

Question 3

“What is the forensic question?”
What are some things to think about in regards to finding the forensic question and how to analyze/examine the evidence?

Answer 3

Always “WHO” is on the evidence
But, we need to figure out “HOW do we get the WHO from the evidence” and what does it mean that the WHO was on the evidence

Question 4

What do you consider when determining the order of examining evidence?

Answer 4

Think of the order of DNA concentration. We try to examine evidence in order of low concentration to high concentration

Question 5

When do you take cuttings as opposed to a swab?

Answer 5

When the evidence material is porous such as a shirt and the evidence can penetrate the porous material

Question 6

What are examples of stuff that you’d take a cutting from?

Answer 6

Clothing items for determination of the wearer, staining on fabric, cigarette butts, and adhesive on envelope

Question 7

When are swabs taken as opposed to cuttings?

Answer 7

When evidence is non porous and or if there is expectation that biological material is on the surface of the porous material

Question 8

What are examples of stuff that you’d take a swab from

Answer 8

Clothing for brief contact (on the exterior), plastic, metal, wood, concrete

Question 9

Where do you take samples on clothing for determining the wearer?

Answer 9

collars, waistbands, sleeve cuffs, and interior hat bands

Question 10

What is the average size of presumptive positive stains that we take through for analysis?

Answer 10

1.5cm2 if possible, extracted as trace

Question 11

What is the size of sample that we take through for determining the wearer?

Answer 11

2.0cm2 extracted as Large Volume

Question 12

What is our screening policy in regards to screening guns based on offenses?

Answer 12

P1, we take one swab from the gun and one swab from the magazine and cartridges
P2 we take one swab from the gun

Question 13

What do we do in regards to multiple cartridge cases?

Answer 13

We group them by caliber and area of collection
In the case of cartridge cases, it is okay if there are multiple packages opened at once
We take one swab from each group of cartridges

Question 15

How do we examine bulk consumable items/artifacts?

Answer 15

For porous items such as cigarettes, knit gloves, ski masks, and hats, we prepare a cutting to retain some of the item and take 1.5cm2 for analysis
For non porous items, take a swab of the entire item(for bottles, take swab from the mouth area)

Question 16

What are things to consider when reading SAK paperwork before examining the evidence within the kit?

Answer 16

Any contact between the suspect and victim
If there has been any consensual sexual contact within the last 72 hours of collecting the evidence
Any changing of clothes
Time between the offense and the collection of the kit

Question 17

What do we consider as intimate swabs?

Answer 17

Swabs from areas of penetration or near areas of penetration

Question 18

What are considered non intimate swabs?

Answer 18

areas of potential contact on the body,

Question 19

What is different in regards to the examination of intimate and non intimate swabs?

Answer 19

For intimate swabs, they are directly forwarded to a differential protocol
For non intimate swabs, we test each one with Acid Phosphatase. If they are POS, they are forwarded to diff protocol. If neg, all swabs for that sample are taken through a trace protocol in the case that the suspects epithelial cells are present with the victims

Question 20

Describe out process for taking swabs from condoms or sex devices?

Answer 20

Take two swabs from each side of the condom.
For sex devices, determine the handle then take one swab from the handle and one swab from the insertion end_-> forward to basic extraction

Question 20

For cases that the bulk clothing or bedding is not ALS POS, where should the item be swabbed if necessary?

Answer 20

For underwear, waistband and interior crotch area since a lot of cases involve digital penetration and or no ejaculation

Question 21

How much of a portion is necessary to take through for tissue samples? Hair samples?

Answer 21

0.5cm2 for tissue 2-3cm of root end for hairs

Question 22

What is serology?

Answer 22

The testing and identification of bodily fluids

Question 23

Name some of the presumptive tests for blood

Answer 23

Alder test, Kastle-Meyer/PHE, Ortholidine, LMG, Tetramethylbenzidine test (TMB), Buaiacum, Aloin, Luminol, Bluestar, Fluorescein, ABA card HemaTrace, and Hemastix

Question 24

Name the confirmatory test for blood

Answer 24

Microcrystalline test (Takayama and Teichmann)

Question 25

What are some of the positive reasons that we use PHE at LSPCL?

Answer 25

Non carcinogen, easy to prepare, it has a higher end of sensitivity compared to other presumptive tests but has fewer false positives. It tests for the presence of hemoglobin in blood

Question 26

What are false positives for PHE?

Answer 26

Chemical oxidants (iron or rust), plant peroxidases, tissue, pus or substances of animal origin, warm/hot test samples

Question 27

What are false negatives for PHE?

Answer 27

Blood on items that have been washed or bleached, blood on items treated with H2O2

Question 28

What cross reacts with the presence of human blood when considering the HemaTrace test?

Answer 28

The weasel family

Question 29

Describe the test process for hematrace?

Answer 29

Place sample in buffer for 10-30 mins based on age of sample, place 3-4 drops on card, wait 10 mins to read results

Question 30

What is the high dose hook effect?

Answer 30

This occurs when excess antigen binds to the stationary antihuman antibody in the T area of the card. It prevents the antibody-antigen complex from binding. It can be overcome by diluting the sample

Question 31

What are presumptive tests for seminal fluid? Confirmatory tests?

Answer 31

Presumptive: ALS, AP, P30 or PSA, ad Florence test; Confirmatory: Microscopy, mRNA

Question 32

What is acid phosphatase?

Answer 32

An enzyme secreted by the prostate gland

Question 33

What are false positives for AP?

Answer 33

Vegetable/fruit juices, fungi, contraceptive creams, vaginal secretions, yeast infections, male urine, (Spermicides cause ap- results)

Question 34

What is Prostate specific antigen?

Answer 34

Glycoprotein found in seminal fluid of humans and some old world monkeys. It can be present in the absence of spermatozoa

Question 35

What is the range of the P30 test? Sensitivity?

Answer 35

Range: 200,000 to 5.5 million ng/ml; sensitivity: 4ng/ml

Question 36

When staining spermatozoa, what are the reagents? What are the characteristics of a stained spermatozoa?

Answer 36

Kernechtrot (red) and Brilliant green; the tail is green , head is red, and the acrosome cap is clear

Question 37

What reagents start the process of presumptive testingon intimate samples?

Answer 37

a 1 hour soak in phosphate buffered saline (PBS) for 30 minutes or longer if the stain is very old

Question 38

What is the purpose of PBS?

Answer 38

It is a non toxic solution that allows cellular materials to come off swabs or cuttings