Crime Lab FAQs
Latent Prints Questions:
Q: What is friction ridge skin?
A: Friction ridge skin is more commonly known as fingerprints. Friction ridge skin is the
skin that is on the palms and fingers of the hand and soles and toes of the feet. Friction ridge skin has
raised ridges and furrows between them; this corrugated surface is designed for grasping and holding items. At
the tops of the ridges there are sweat pores. The ridges do not simply start on one side of the finger and
travel straight and uninterruptedly to the other side of the finger but rather these ridges stop, start, and
branch into multiple ridges to form unique and individual patterns. Friction ridge skin forms in the 12th to
16th week of fetal development, and except for changing in size due to growth, remains the same throughout a
persons life until decomposition.
Q: What is a latent print?
A: A latent print is a chance or accidental reproduction of some area of friction ridge
skin; by definition, "latent" means hidden or not visible. The pores at the tops of the friction ridges are
constantly exuding water and waste products, which cover the friction ridges. When items are touched, this
moisture, along with any other contaminates are deposited on the surface of the item in the pattern of the
friction ridges, not unlike a rubber stamp. Since the latent print is not visible some development process
must be used to make the latent print visible.
Q: What is a known print?
A: A known print is a deliberate reproduction of some area of friction ridge skin. This is
most often done by applying printers ink to the fingers or palm and placing them on a white fingerprint
card, producing a reproduction of the friction ridge pattern.
Q: Why are fingerprints used for identification?
A: The two principals used for fingerprints as a positives means of identification are
that fingerprints are permanent and unique. This means that an area of friction skin of an individual will
not be duplicated on their own hands or feet nor on any other person's hands or feet.
Q: How are fingerprints compared and identification made?
A: The stopping, starting and branching into multiple ridges occur randomly. These form
the individual ridge characteristics that examiners look for. An examiner will do a side-by-side comparison
of the unknown, or developed latent print against the known print. This is usually done by using a
five-power magnifier. The examiner looks for the same type of individual ridge characteristic, in the
same location, in both the unknown and known prints. These individual ridge characteristics must be in
the same unit relationship to each other, for instance if there are two ridges between two ridge
characteristics in the unknown print, there must be two ridges between the same two ridge characteristics
in the known print. If there is a sufficient quantity of those individual characteristics found with no
unexplainable differences, then the examiner can state that the same person made the developed latent
print and the known print. This is to the exclusion of all other persons.
Q: How long will fingerprints last?
A: There is no scientific way to know how long a latent fingerprint will last. Fingerprints
have been developed on surfaces that had not been touched in over forty years; yet not developed on a surface
that was handled very recently. There are a multitude of factors that effect how long fingerprints last. Some
include the type of surface touched; the individual who touched it, and environmental conditions can have
serious bearing on how long a fingerprint will last on a surface.
Q: Can you tell how old a fingerprint is?
A: There is no scientific way to date the age of a developed latent fingerprint. The only
possible way to know the approximate age of a latent fingerprint is to know the last time that the surface
that the developed latent print is on was thoroughly cleaned. Generally latent print residue will not
survive a thorough cleaning, so if a latent print is developed it was probably deposited after the cleaning.
Q: Do identical twins have the same fingerprints?
A: No, no one has the same fingerprints; although identical twins have the same DNA, they
have different fingerprints.
Q: What can fingerprints be recovered from?
A: Under the right conditions latent prints can be recovered from almost any
surface. As technology advances the opportunities to recover latent prints has also advanced; so that now
surfaces that would not have been checked for latent prints years ago routinely yield latent prints.
DNA Analysis Questions:
Q: What kind of blood tube is needed for DNA analysis?
A: A purple-capped (EDTA) blood tube is preferred. Alternately, a buccal swab (swabbing of
the interior cheek) may be used as a reference standard.
Q: What does the expiration date on the sexual assault kits mean, should they be thrown out if they are expired?
A: The expiration date on the sexual assault kit refers to the blood tube only. If the blood
tube has expired replace it with a purple-capped (EDTA) blood tube from the hospital stock. Do not discard the kit!
Q: Why do I need to submit standards from my suspect(s) and victim(s)?
A: It is incumbent upon the DNA section to make every reasonable effort to associate biological
stains with the individuals who may have imparted the stain. Due to the sensitivity of current DNA procedures, it
is not uncommon to find mixtures of DNA on an item. An example of this would be finding the suspect's blood on
the victim's clothes. Simply being the wearer of the clothing, the victim may impart their own DNA on the
garment, thus causing a mixture with the suspects DNA. If we only had the suspects standard to compare to the
stain, there would always be a question as to who else's DNA is present unless we had a standard from the victim as well.
Q: What is meant by a standard?
A: A standard is a reference biological specimen from a known individual. Obtaining a standard
from a known individual is similar to obtaining a ten-print card for fingerprint comparison. Intravenous blood
and buccal swabs (swab from the interior cheek) are appropriate standards to use for comparisons.
Q: What is a secondary standard and why don't you use secondary standards for comparison?
A: A secondary standard is a reference standard that is not an intimate sample such as
intravenous blood or buccal swabs (swab from the interior cheek). Secondary standards are normally items
that have used by the person such as a toothbrush, used dental floss, shaving razor and or a cut from a
suspects hand. We generally do not like to use these items as standards because we cannot always ensure
that these items came from the person in question. If an appropriate standard is available we will always
request that over a secondary standard. In circumstances where an appropriate standard is not available, such
as missing persons, mass disasters or interred bodies, we will consider using a secondary standard.
Q: Will you come to the crime scene and collect the evidence?
A: Although we do not have the capacity to come to every crime scene, we are available to
assist in unusual situations.
Q: What type of education is required for employment?
A: The DNA section requires its analysts to possess a baccalaureate degree in one of the
natural sciences (eg. Biology, Chemistry, Forensic Science); coursework must include 20 semester hours in
biology (course credit in genetics, biochemistry, molecular biology, recombinant DNA technology or other
subjects which provide a basic understanding of the foundations of forensic DNA analysis should be included
in hours. Course credit in statistics and/or population genetics is recommended.
Q: How do I submit evidence to be tested by the laboratory?
A: The MSHP Crime Laboratory Division will accept evidence from any law enforcement
agency, regulatory agency, or law enforcement function branch of an agency in or of the State of Missouri
or the Federal Government of the United States. All evidence received must be associated with a criminal
investigation. Evidence associated with civil litigation will not be accepted. DNA evidence and convicted
offender blood samples will be accepted according to the criteria outlined in the MSHP DNA Profiling Service
Pamphlet and RSMo 650.055. Law enforcement agencies and crime laboratories requesting DNA profiling searches
on forensic crime scene samples or offender information will be required to submit their request according
to the MSHP Guidelines for Convicted Offender Sample and CODIS Database Usage. All evidence received by the
Highway Patrol Crime Laboratory must have a proper seal installed. A proper seal is defined as closure of
the container by any number of various sealing devices which will protect the contents from loss, cross
transfer, contamination or degradation during routine handling. The seal should be such that entry into the
container will result in obvious damage and/or alteration to the container or its seal and is further
authenticated by the initials or identifying mark of an individual responsible for the container's
contents. Evidence that is too large to be sealed (vehicle body parts, mattress, house doors, etc.) will
be stored in a secure area of the laboratory and examined as soon as possible. The Laboratory will not
repeat or duplicate forensic examinations that have previously been performed by another laboratory not
affiliated with the MSHP Laboratory System. Supplemental testing that has not been performed on previously
examined specimens will be conducted only if a copy of the original laboratory's report accompanies the
submitted evidence. The Laboratory will not repeat or duplicate forensic examinations that have been performed
by any member of the staff of the MSHP Laboratory System. The exceptions to this policy are those occasions
when re-examinations are performed as a quality control check or the examiner's casework is being evaluated
as part of a documented corrective action. Generally all evidence, and samples collected from evidence, will
be returned to the submitting agency when the forensic examinations are completed. With written authorization
and the signature of the individual from the submitting agency who is responsible for the evidence, the
laboratory staff may dispose of coroner or medical examiner blood samples, Drug Recognition Expert (DRE) training
samples, and Liquor Control regulatory beverage samples if so directed. A Disposition of Evidence form
(pink sheet), a signed letter, or other signed documentation from the submitting agency requesting samples to
be destroyed will be maintained in the case file. Any markings that identify a victim or a suspect will be
removed or permanently obliterated from the sample before it is destroyed. All items will be disposed of safely
Q: Do you do paternity testing on criminal cases?
A: Currently we do not perform paternity testing. We will however DNA type samples in criminal
cases where paternity may be an issue.
Q: Can I use tap water to collect a bloodstain?
A: The appropriate and preferred source of water would be distilled water on a sterile
swab. Bottled water purchased at a convenience or grocery store may be considered distilled. If an appropriate
water source is not available, tap water would be acceptable.
Q: Why does it take so long to get the results of my case?
A: The DNA section of the MSHP Lab services 114 counties and over 300 municipalities. As a matter
of routine, we work cases on a sequential basis. Often times it may be several months in duration before we
actually begin a particular case. If a case necessitates being expedited, please contact the laboratory director
to present your request.
Q: Why don't you just do DNA on all of my samples, not just the ones you pick?
A: DNA evidence is best used to make good associations between victims, suspects, and
crime scenes. As DNA testing is very expensive, it is our position that we generate as many associations
as possible using the least amount of resources and evidentiary material.
Q: Why do the reports contain so much unnecessary information...all I want to know is it a match or not.
A: Due to our accreditation and laboratory policy, we are required to include much more
information in our reports than may seem necessary to the casual observer.
Q: What is meant by the term match or consistency?
A: We report that two samples are consistent with each other instead of using the term
match. Although the words consistent and match may mean the same thing to most individuals, we usually try
to avoid the term match because it may misrepresent the samples as being the same. Typing the DNA essentially
comes down to doing a comparison between what is observed in the unknown specimen to what is observed in the
known specimen. When we report DNA results we are reporting on only a small portion of the DNA molecule. Without
typing the entire DNA molecule from end to end we cannot say with 100% certainty that the samples match, only
that they are consistent with each other at the area of the DNA molecule that was compared.
Q: What do the statistics in my report mean?
A: Since we do not look at the entire DNA molecule and only look at a small portion, we apply
a frequency statistic on the genetic loci (locations) that were observed in order to give us a statistical measure
of how often we could expect the observed genetic pattern or profile. In other words, we attempt to report
statistically how frequent or rare it would be to randomly encounter the questioned genetic profile (or pattern)
at all of the genetic areas tested. This type of estimation is very similar to various statistical measures many
of us may use in our daily lives, such as knowing that the frequency of obtaining a heads when a coin is flipped
would be 1 in 2; or obtaining a six on a six-sided die would be 1 in 6.
Q: Why can't I package items in plastic?
A: Biological specimens inherently harbor bacteria. Bacteria grow in warm and moist
environments. Packaging biological specimens in plastic would encourage bacterial growth by allowing the
specimen to stay warm and moist, a greenhouse effect. Packaging in paper (or cardboard) will allow the
specimen to breathe and will take away the one thing that bacteria need most, moisture. Packaging in paper
and keeping the specimen cold (or frozen) is the most suitable way to attenuate bacterial growth.
Q: Can DNA analysis be done on hair?
A: Yes, hair does contain DNA. Due to the cost of DNA analysis, we recommend question hair and a
hair standard be submitted to the lab for microscopic hair comparison first. If the hair examiner finds the question
hair similar to the hair standard, DNA may be recommended. If the root of the hair is in it's active growing
stage, DNA may be extracted from the root. If the root is not in it's active growing stage and naturally shed, then
the hair would be a candidate for mitochondrial DNA analysis. The Highway Patrol lab DOES NOT perform mitochondrial
Q: What is mitochondrial DNA testing?
A: The MSHP Crime Laboratory performs DNA testing on DNA extracted from the nucleus of the
cell. Mitochondria are organelles in the cell that maintain their own autonomous genome. Mitochondria are in
much greater abundance than the nuclei of the cell and therefore biological specimens will contain much more
mitochondrial DNA. In particular, hair and bone tissue that do not contain nuclei and therefore do not have
nuclear DNA and would subsequently lend themselves well to mitochondrial DNA testing. A distinct advantage of
mitochondrial DNA testing is that the mitochondrial genome is maternally inherited and does not undergo
recombination (hemizygous); therefore the mitochondrial DNA is very useful in comparing maternal lineages. This
can be very valuable in missing person's cases or found body cases. If mitochondrial DNA testing is recommended
the MSHP laboratory will assist in obtaining that testing.
DNA Profiling Questions:
Q: Who is required to provide a DNA sample for entry into the Missouri DNA Data Bank?
A: Any individual who is found guilty of a felony or any offense under 566, RSMo. Also, any individual who is seventeen years of age or older and is arrested for burglary in the first degree under section 569.160, RSMo, or burglary in the second under section 569.170, RSMo, or a felony offense under chapters 565, 566, 567, 568, and 573, RSMo, is required to provide a biological sample for DNA analysis. Additionally, any individual who has been determined to be a sexually violent predator pursuant to sections 632.480 to 632.513, RSMo, or who is required to register as a sexual offender under sections 589.400 to 589.425, RSMo, will be profiled for the DNA database.
Q: What is CODIS?
A: CODIS stands for Combined DNA Index System. It is a national system of computer
databases designed by the FBI to store DNA profiles from convicted offenders, crime scene evidence, as
well as missing persons. Any DNA profile developed from the evidence in a case can then be searched against
the databases, and possible investigative leads may develop from any matching profiles in the database.
Q: On what types of cases can a CODIS search be conducted?
A: CODIS searches can be conducted on the DNA profiles developed from biological evidence in
any criminal investigation. In theory, any biological material could yield a DNA profile if there is sufficient
quality and quantity of sample from the perpetrator.
Q: What does a CODIS hit mean?
A: A CODIS hit can be made by a DNA profile from evidence matching the DNA profile from a
convicted offender. A hit can also be made between evidence in one case matching the DNA profile of another
case. The match of the DNA profiles provides an investigative lead to the detective or investigator. The
investigator will conduct further investigation to determine if the involvement of the convicted offender
has any punitive value.
Q: How long will the DNA profiles stay in CODIS?
A: The DNA profiles will be maintained in the system indefinitely, barring any legal requirement
to remove the profile.
DNA Profiling Law Enforcement Questions:
Q: How can I get my case searched in CODIS?
A: If you have biological evidence believed to be from the perpetrator of a crime and a DNA
profile is developed, the profile will automatically be searched against the DNA database in Missouri and
nationally. The sample will remain in the database and be continually searched against the growing database. If
there is a hit against a convicted offender or another case, you will be contacted and provided with the
offender's name or the name of the investigator of the other case.
Q: How can I get my case searched against other states?
A: If the DNA profile is of sufficient quality it will automatically be shared with all the
states in the US. A match may occur with an offender or crime scene sample from another state.
Q: How can I find out if a particular individual is in the database?
A: Send a written request on departmental letterhead to the Crime Laboratory CODIS
Administrator. Include as much identifying information about the individual as possible in the letter, such
as full name, date of birth, and social security, Department of Correction's or State Identification
numbers. In order to obtain information about an offender from another state, the request must be sent to
that state's CODIS Administrator. You may contact us for assistance.
Q: What type of tube should be used to collect blood?
A: Grey stoppered tubes are highly recommended by the laboratory. These tubes typically have two preservatives, sodium fluoride and potassium oxalate which help prevent clotting as well as microbial action. The laboratory only accepts grey stoppered tubes for blood alcohol testing.Q: What specimen is best to collect for toxicology testing ?
A: Blood is best to help determine which drugs were present during the time of an incident. Active drugs, that is drugs that have a physiological effect on the body, can present as possible indicators of impairment in blood. Urine on the other hand is only indicative of past usage and does not necessarily reflect presence at the time of the incident. Urine however is typically easier for an agency to collect whereas a trained phlebotomist is necessary to draw blood.Q: Do drugs in the blood prove impairment ?
A: No, the presence of a drug or drugs in blood do not necessarily prove impairment of the individual. Several factors including dosage, metabolism and tolerance all play an important role in an individual's possible impairment by a drug or drugs. Officer observation remains the best source of proving impairment.Q: What are the storage requirements for collected specimens?
A: Urine samples should be refrigerated or frozen within 24 hours of collection. It is best practice to refrigerate blood samples upon collection.Q: How many blood draws should be collected for blood alcohol testing?
A: Only a single draw is necessary for blood alcohol determinations. When alcohol back extrapolations are performed in court, toxicologists routinely base their estimations off the value of the first blood draw and do not factor in subsequent blood draws. Second and even third blood draws are not necessary.
Q: What does the reporting limit mean on a blood alcohol report?
A: The stated reporting limit is the lowest value or limit of quantitation that would be reported. Results below the reporting limit of 0.010% will be reported out as negative for ethyl alcohol.