Interviews

Stephanie Stoiloff, M.S.
Criminalist
Miami-Dade Police Department
Miami, Florida
E-mail: sstoiloff@hotmail.com

How did you become a forensic scientist?

My 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?

The best part of this work is working with the detectives to solve a crime as well as teaching the power of DNA technology.

Has a suspect ever been convicted based on your DNA analysis?

A 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?

DNA 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?

In 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?

Again, 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 you found?

Personally, I have not yet encountered a situation where a verdict has been reversed because of new DNA evidence that I have found.

What do you look for in a DNA test? How do you know when a "match" is found or when a suspect is "guilty" or "innocent"?

After 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".

The 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.

On 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.

My 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.

Some 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?

The 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?

Personally, 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 expedite adjudication.

How is a DNA sample collected?

A 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).

A 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.

Stephanie Stoiloff
E-mail: sstoiloff@hotmail.com