Stephanie Stoiloff, M.S.
Miami-Dade Police Department
How did you become a forensic scientist?
interest in forensic biology started when I was in college.
I did some research into the field while working on my
Bachelor's degree. While I was working on my Master's
degree, I was an intern at the Miami-Dade Police Department
Crime Lab and that job only fueled my interest. I actually
started working here in a full time position of Criminalist
in the Forensic Biology Section in June of 1998.
What's the most exciting and rewarding part of your work?
best part of this work is working with the detectives
to solve a crime as well as teaching the power of DNA
Has a suspect ever been convicted based on your DNA analysis?
suspect has been convicted based on DNA analyses that
I have performed; however, DNA analysis is only a part
of the evidence in a case. The jury would decide what
weight is given to this evidence. I have performed DNA
analyses that have been used in trial, but I do not usually
have knowledge of what a jury decides or how they arrive
at their decision. Many times we do not even know the
outcome of a case.
Why is DNA more accurate than a fingerprint?
evidence is different from fingerprints. Most criminals
are aware of leaving fingerprints behind at a scene and
therefore try not to leave such evidence. DNA, on the
other hand, can be obtained from so many different objects
and/or sources that there is a greater chance of obtaining
a DNA profile. Both fingerprints and DNA are used for
the purpose of identification.
Why do you use PCR testing instead of RFLP testing methods?
our crime laboratory, we use Short Tandem Repeat DNA Analysis
or STR DNA Analysis. This method uses PCR in the DNA analysis
process. PCR based methods of analysis typically require
much less DNA to start with than RFLP so the original
evidence sample can be very small if not invisible. In
addition, the STR analysis method is much faster and our
turn around time for results is about 3-4 weeks in comparison
to 3-4 months for RFLP.
Can a Florida jury convict a suspect solely on the basis
of DNA evidence?
since DNA is usually only part of the evidence in a case,
I do not know if you can ever say that a conviction is
solely based on one piece of evidence. However, if DNA
results were the only evidence, the jury would decide
the weight of the DNA.
Has a verdict ever been reversed because of new DNA evidence
I have not yet encountered a situation where a verdict
has been reversed because of new DNA evidence that I have
What do you look for in a DNA test? How do you know when
a "match" is found or when a suspect is "guilty"
samples for a case are processed, the resulting DNA profiles
from both the evidence samples and the standard samples
are compared. Keep in mind that the standard samples are
samples from a known source and the evidence samples are
considered to be of unknown origin. If the sample(s) of
unknown origin have the same DNA profile as a standard
sample that is provided, these would be called a "match".
circumstances of the case would determine if a suspect
is exonerated or implicated. For example, in a sexual
battery case, the evidence profiles may not show any male
profiles and the only match would be to the victim. In
this scenario, there would be no suspect profile and therefore
no way to prosecute a suspect based on DNA evidence.
the other hand, if the analysis on a sexual battery case
produced an evidence sample with a male profile and a
suspect standard sample with the same profile, this would
be called a match. If the suspect standard sample produces
a DNA profile that does not match the DNA profile from
the evidence sample, then this would not be a match and
the suspect would be exonerated.
job as a DNA analyst is not to determine guilt or innocence--that
is for the courts to decide--but to report on the evidence
that I analyze.
police agencies throughout the United States have begun
collecting DNA samples from all sex offenders. Others
want to collect DNA samples from everyone who is arrested,
as means of identification. Do you agree with this? Why
or why not?
state of Florida collects DNA samples from select convicted
offenders (this depends on the offense) and has done so
since 1990. In the United Kingdom, DNA samples are collected
from all arrestees. In my opinion, DNA samples should
be taken from all arrestees; this sampling method would
greatly assist in the number of criminals who could be
identified. Data has shown that criminals escalate from
robbery and burglary to other more serious crimes; if
these individuals are profiled and put into our database
when they start out in their criminal careers, we could
identify them much faster.
Do you believe that the collections mentioned above are
unconstitutional, as some civil liberties unions claim?
Why or why not?
I do not believe that the DNA sample collection is unconstitutional.
It is my belief that the laws for collection could be
set to minimize abuse of the system. An interesting comment
was made at a recent meeting I attended: what happens
to the blood that we give at the doctor's office? Does
anyone really know? Do we sign any papers when we give
this blood? Another thought to ponder is that fingerprints
are routinely requested as identification for all types
of documents. Why are DNA profiles treated so differently?
If certain laws are created to ensure that the DNA samples
would be utilized for database use only, there would be
no reason to call this collection unconstitutional. One
thought that is often forgotten is that this enlarged
collection of DNA samples can only help solve crimes and
How is a DNA sample collected?
standard DNA sample is typically collected as a tube of
blood (i.e. from the Medical Examiner's office, from the
jail, etc.) or a buccal swab (use a cotton swab to collect
the epithelial cells on the inside of your cheek).
DNA evidence sample can be practically anything that is
considered evidence in a particular case. How these samples
are collected depends on what the item is. For example,
a sheet on a bed could have evidence and crime scene will
usually remove the whole sheet so that a more thorough
inspection can be done in the laboratory. Items that are
typically collected include clothing, weapons of all shapes
and sizes, and rape kits (collected at the Rape Treatment
Center). Keep in mind, however, that evidence can be almost
anything found at a crime scene.