Microscopy, Forensic Biology, and Sexual Assault Evidence: Key Concepts and Techniques

What is a simple microscope?

A magnifying glass.

What is the basic microscope of forensic science?

The compound microscope.

What are the two main lenses of a compound microscope?

Objective lens and ocular (eyepiece) lens.

What does parfocal mean?

Once focused with one objective, another objective can be rotated in and the specimen remains in focus.

What is the function of the illuminator?

The provides the microscope with a light source.

What is the function of the condenser?

Focuses light onto the specimen.

What is the function of the objective lens?

It is the first image-forming component.

What is the function of the ocular lens?

It is the final image-forming component.

What does field of view mean?

The area that can be seen through the eyepiece.

What does depth of focus mean?

The thickness of the specimen that can be seen clearly.

How do you calculate the total magnification of a compound microscope?

Ocular magnification × objective magnification.

What is total magnification with a 10× ocular and 20× objective?

200×.

How does an image appear through a compound microscope?

Inverted.

What are the common types of microscopes listed in the lecture?

Compound, comparison, stereomicroscope, polarizing, microspectrophotometer, and FTIR.

What is a comparison microscope?

Two compound microscopes connected by mirrors and prisms so two objects can be viewed side-by-side.

What is the main purpose of a comparison microscope?

To compare two different objects side-by-side.

What can be changed while viewing evidence with a comparison microscope?

The view can be emphasized from one side to the other.

What is the general magnification range of a stereomicroscope?

10× to 125×.

What type of view does a stereomicroscope provide?

A 3D, right-side-up image.

What does a microspectrophotometer determine?

The color spectrum of a microscopic object.

What does a microspectrophotometer determine?

The color spectrum of a microscopic object.

What type of light can a microspectrophotometer use, and which is most commonly used in labs?

Visible/UV; most labs exclusively use the visible spectrum.

What evidence is a microspectrophotometer most commonly used to examine?

Fibers and paint chips.

Besides drugs, what can FTIR determine?

The chemical composition of fibers, plastics, and paint chips.

What was forensic biology originally called?

Forensic serology.

What was the purpose of traditional forensic serology?

To use serological techniques to determine the possible origin of body-fluid stains.

What types of methods are used in modern forensic biology?

Chemical tests, molecular biology, population genetics/statistics, computer algorithms, crime-scene reconstruction, and bloodstain-spatter interpretation.

What major crimes commonly involve forensic biology?

Homicide, assault, sexual assault, and burglary/robbery.

What are the three homicide charge categories listed in lecture?

Murder, manslaughter, and criminally negligent homicide.

What makes a killing murder according to the lecture?

The person intends to cause death and causes that person's or a third person's death.

What makes a killing second-degree manslaughter?

Recklessly causing another person's death.

What makes a killing first-degree manslaughter?

Intending to cause serious physical injury, but causing that person's or a third person's death.

What does criminal negligence mean?

Failure to perceive a substantial and unjustifiable risk, a gross deviation from reasonable care.

What is criminally negligent homicide?

Causing another person's death through criminal negligence.

What is rape as defined in the lecture?

Nonconsensual vaginal/anal penetration by a body part/object, or oral penetration by another person's sex organ.

What is statutory rape as defined in the lecture?

Sexual intercourse where the victim is below the age of consent and perpetrator is above it.

What is sodomy as defined in the lecture?

Nonconsensual anal or oral copulation with a member of the same or opposite sex.

What percentage of rape victims listed in lecture are female?

86%.

What percentage of rape victims listed in lecture are male?

14%.

What percentage of rape victims received an injury in addition to the rape?

38%.

What percentage of rapes in the lecture data were reported to police?

36%.

What reasons does the lecture give for sexual assaults going unreported?

Considered a personal matter, fear of reprisal, and perceived police bias.

What is an element of every sex offense?

Lack of consent.

What three situations can result in lack of consent?

Forcible compulsion, incapacity to consent, or not consenting.

Can a minor who is capable of giving informed consent consent to sexual-assault treatment?

Yes.

Can a minor who can give informed consent be forced to undergo a sexual-assault exam?

No.

How must a consenting minor's sexual-assault treatment be handled?

Confidentially, like any other patient.

Who does the lecture consider incapable of consent?

Someone <17, intellectually disabled, mentally incapacitated, physically helpless, or in the specified institutional situation.

Should a reporting sexual-assault patient still be examined if significant time has passed?

Yes. All reporting patients should be examined regardless of elapsed time.

Who usually performs a specialized sexual-assault examination?

A SANE — Sexual Assault Nurse Examiner.

What is the purpose of a Sexual Offense Evidence Collection Kit?

To collect and preserve evidence from a sexual-assault victim.

What type of kit should be used to maintain chain of custody?

A sealed kit with a sealed inner plastic bag.

What information must be written on each evidence item from the kit?

Patient name, date, collector name/initials, description, and specimen source.

What must every person who handles the sexual-assault kit record?

Their initials, date, and time.

How should a sexual-assault kit be resealed after opening?

With tamper-evident tape, and the new seal must be initialed.

Why is forensic photography important when documenting physical evidence?

Physical evidence can be short-lived; photographs provide a permanent record.

How should bite marks be photographed?

Extensively, using scales and special lighting, with the injury clearly visible.

Should a bite mark be photographed before or after swabbing?

Before swabbing.

How is biological evidence collected from a bite mark?

Swab with sterile deionized water, place in a dried-secretions box, and label it as a bite mark.

What specimens should be collected ASAP in suspected drug-facilitated sexual assault?

Urine and blood for toxicology.

Why is clothing collected over examination-table paper?

The paper catches trace evidence that may fall from the clothing.

What clothing should be collected after a sexual assault?

Clothing worn during or immediately after the assault.

How should individual clothing items be packaged?

Separately in paper bags.

Should clothing evidence be stored long-term in plastic bags?

No it should not.

What should be done with wet stains on clothing before final packaging?

Allow them to air dry.

If clothing must be cut off the victim, what should you avoid cutting through?

Existing tears or holes.

How are fingernail scrapings collected?

Scrape each nail over paper; use a separate paper towel for each hand and include the scraping stick.

How are pubic-hair combings collected?

Comb over a paper towel beneath the pubic area, then place the comb on the towel and fold it.

Do pulled-hair standards have to be collected immediately?

No. Collect during the exam if possible with minimal trauma, or later if required.

How many swabs are collected from each oral, anal, vaginal, and cervical site?

2 from each site.

What should be done if matted head or pubic hair is found?

Ideally cut it off, place it in a debris collection envelope, and label its source and reason for collection.

How long does the law described in the lecture require designated sites to store rape kits?

20 years.

What is the first important step when biological evidence arrives at the lab?

Documentation.

What should the analyst document about evidence in the lab?

Packaging condition, evidence condition, stains present, and test results.

What information must appear on every page of an analyst's lab notes?

Page number, case number, date, and analyst initials.

How should an analyst correct an error in laboratory notes?

Draw a single line through it and initial it.

What future testing should be assumed when collecting biological samples in the lab?

Assume DNA typing will be performed.

Why should a new clean cutting surface be used for each evidence item?

To prevent contamination between evidence items.

How should forceps be cleaned before collecting biological evidence?

Clean with 5–10% bleach, followed by flame.

What should be used to cut each separate evidence item?

A clean scalpel for each item.

What should be done to a stain before removing it from an evidence item?

Photograph/document it.

What information about a stain should be documented before removal?

Its description, location, and size, with a clothing diagram when appropriate.

What five types of biological stains are covered in the lecture?

Blood, semen, saliva, urine, and feces.

What are the three cellular components of blood?

Red blood cells, white blood cells, and platelets.

What is the liquid portion of blood called?

Plasma.

What are presumptive approaches/tests for blood?

Appearance, phenolphthalein, leuco-malachite green, and luminol.

Does blood fluoresce under a monochromatic light source?

No.

What is the chemical name for luminol given in the lecture?

3-aminophthalhydrazide.

What is luminol used to detect?

Occult blood, especially blood that may have been cleaned up.

What does a positive luminol reaction produce?

It produces an emission of light.

Why must luminol testing be performed in the dark?

Because a positive reaction is detected by its emission of light.

What makes luminol useful for searching a large crime scene area?

It can be easily sprayed over a large area.

What is a major limitation of luminol?

It cross-reacts with many compounds, including cleaning agents and metals.

After identifying blood, what must be determined next?

Species of origin.

What two methods are used for species identification?

Antiserum-based and DNA-based methods.

What does antiserum-based species identification use?

Species-specific precipitating antisera.

How is the Ring Precipitin Test performed?

Layer bloodstain eluate over antiserum, keep vertical for 10 min, then examine the interface.

What indicates a positive ring precipitin test?

A thin white ring at the antiserum/eluate interface, best viewed with bright light.

What is semen composed of?

Spermatozoa in secretions from several male reproductive glands.

What glands contribute secretions to semen?

Prostate, seminal vesicles, Cowper's gland, and glands of Littre.