The Use of Forensics in the Courtroom

By Christine Funk

Using forensic science in the courtroom can have a fantastic effect on jurors, when done properly. When not done properly, it can be a fantastic failure. So how is a lawyer to know the difference? It is true that, as one of my mentors often said, “Even a blind pig finds an acorn once in a while.” For example, in 1993, as a law clerk for the Dakota County Attorney’s Office, I prepared for my first trial—a juvenile speeding ticket. Someone in the office kindly “gave me the questions” for laying the foundation for the calibration of the radar gun. I dutifully read them off, word for word and in the order they appeared, and the record came in. It is no longer quite that easy. As a general rule, attempting to use forensics in a courtroom setting without adequate preparation usually results in crashing and burning in a most spectacular fashion. Proper use of forensic science begins long before the “courtroom scene.”

Forensic Science and Discovery

Proper use of forensic science, whether as a prosecutor, plaintiff, or defendant, starts with discovery. When a report is generated containing forensic science conclusions, lawyers must be aware scientists do not create these reports out of whole cloth. Rather, there is data, some submitted to the scientist, some perhaps generated by the scientist or the instrumentation at the lab; and there are interpretations of that data.  Without demanding the underlying data, one cannot begin to competently question the scientist about the conclusions they have drawn.

Ask for the File

When a scientific conclusion (or a conclusion that no conclusion can be reached) comes from one of Minnesota’s crime laboratories, lawyers can ask for the underlying data used to support their conclusions. This is commonly referred to as “the file.” The crime laboratories in Minnesota have Standard Operating Procedures governing what steps must be documented in their files.

Similarly, when a fire inspector writes a report, there is “a file” (or there should be) documenting the work of the fire inspector. For fire investigations, the National Fire Protection Association (NFPA) 921 governs. It calls for such things as “copies of notes taken at the scene.” Likewise, the National Association of Medical Examiners (NAME) have certain requirements for autopsies. When laboratories fail to comply with the requirements of their governing body, they can lose accreditation or, in the case of public health labs, their certification. 

Ask for the Narrative

The “narrative,” sometimes referred to as the “communications log” or the “com-log” or some other variation, documents all communications between the lab and any outside persons. For years I asked for “the communication log” and was told no such log existed. Ask the lab where they document communications with outside persons and ask for a copy of it.  

It should include all communications pertaining to the case. Examples I have personally seen include a call from a U.S. Attorney telling a lab analyst they “had to” find the defendant’s DNA in a rape sample, because he was a really bad guy, and they knew he had raped someone else in the neighborhood—a case they couldn’t process because the victim was not documented. I have also seen a police department submit a request to “find the defendant’s DNA on the gun.” Who can forget the famous Duke lacrosse case, in which the now-disbarred prosecutor famously asked the lab to change the wording of a report? That information didn’t come to light because of a diligent prosecutor or a concerned plaintiff’s attorney. It came to light because a defense attorney with little to no training in DNA evidence asked for the file and reviewed the communication logs. Sometimes, the documentation of communications runs more mundane, such as the need to move a trial date because a witness is unavailable. Oftentimes the communications log can provide helpful information to all the attorneys involved. But they do have to look at it. Which means they have to ask for it. 

Ask for Other Documents

Forensic science is fallible. Sometimes things go wrong. Sometimes things go exactly right and still a result is “wrong.” Consider, for example, a DNA analyst’s own DNA ending up in a crime scene sample they are testing. Is the analyst arrested and charged? Much to the relief of most forensic scientists, the answer is usually no. Sometimes, a DNA sample can get contaminated—due to careless evidence handling, or because the testing is so sensitive that even a few cells can result in a DNA profile. Most labs keep track of these incidents, often referred to as “unexpected results.”  There is value in keeping track of these unexpected results. It’s not just analysts whose DNA can show up in test results. Janitors, law enforcement, and unidentified profiles sometimes just “show up.”  

You may want to ask about the maintenance of the instruments in the lab. How often, for example, are they calibrated? How often are there problems? In one drug crime lab, the data regarding the maintenance of the instruments relied upon for drug testing reflected extremely frequent service for “white stuff” clogging the intake instrument. Draw your own conclusions.

Finally, labs that are accredited only receive such accreditation after scrutiny. And with scrutiny comes data. You can ask for the underlying data. Note: Often there is a preliminary audit and a final audit. Ask for both. You may learn something mundane, such as that no one there has CPR training. Or you may learn something appalling, such as that an analyst keeps reagents at her desk without regard to expiration dates. Or that property has a strange way of moving from one shelf to another with no accountability.

Ask for CVs for all Scientists

NFPA, for example, has a list of educational requirements for those involved in evaluating fire scenes. It can be found in NFPA 1033. Other professions have similar requirements. Vet the CVs first to assure yourself they are, indeed, qualified to perform their duties. Additionally, in this day of documented fraud cases across the country, an attorney would be remiss not to confirm the education and experience listed on the resume. In 2012, Annie Dookhan, a drug chemist, was charged with obstruction of justice, tampering with evidence, perjury, and falsification of academic records. In both her resume and in testimony, she claimed to have a master’s degree in chemistry from the University of Massachusetts Boston. She didn’t. This behavior covered a span of years, including before Melendez-Diaz v. Massachusetts,1 wherein the Massachusetts Attorney General argued to the United States Supreme Court that there was no need to cross-examine the scientist, as the reports of forensic scientists were “not accusatory.”

Ask for the Employee File

In Minnesota, subject to certain exceptions, the employee files of employees of government entities are discoverable under Minnesota Statute 13.43 subd. 2.
In Bullcoming v. New Mexico,2 a supervisor appeared to testify about the DWI blood test results generated by another scientist in the lab. Notably, in rejecting the substitution, the court opined that the defense attorney may have been interested in exploring why the scientist was on a two-week unpaid suspension from his lab duties. Was it for faking test results? Lying about credentials? Stealing drugs from the crime lab? Without the employee file, the attorney may never know.

Meet with the Analyst

Regardless of what you think the report means, make an appointment to meet with the forensic scientist. Some attorneys believe there is an advantage to meeting with the analyst privately. Others find an advantage meeting with the attorney for the other side as well as the analyst. In one of my favorite closing arguments of all time, a friend of mine started with the observation that “Science doesn’t have an agenda.” This should be true in every case. A forensic analyst has ethical obligations, as outlined by their laboratory. Associations such as the American Academy of Forensic Sciences (AAFS), the International Association for Identification (IAI), the American Board of Criminalistics (ABC), and NAME also have codes of ethics their members are expected to adhere to. 

Meeting with the analyst provides lawyers with the opportunity to ask whatever “dumb questions” they think they have. For the record, however, forensic scientists are already aware that many lawyers are “good with math” and “don’t like science.” Overall, my personal experiences meeting with analysts has been positive. In the beginning of my career, I would try to shield my purpose. But as I have developed as an attorney in recent years (and as one who embraces the theory that science doesn’t have an agenda), I have made it my practice to simply go to the lab and ask the analysts the questions I plan to ask them at trial. When

they don’t answer as I think they were going to, this is a chance for extended discussion.

Consider Getting Your Own Expert

Your own expert may also be of help in deciphering the file. They may be able to point you to a relevant study or notice a particular fact that is of issue in the case. Some experts consult. Other experts testify. Understand the difference. 

If You Are Going to Use an Exhibit, Talk to the Analyst About it Ahead of Time

Do not ask an analyst about a study they haven’t seen. Do not send an analyst a study and ask them to read it, then question them about it on the stand for the first time.  Do not ask an analyst to perform a demonstration without talking to them about it first.

Instead, do discuss any potential exhibits you plan to use. Personally, I have introduced crime scene photos, sketches of arson fires, handwritten notes, and drawings of the particular location of a blood-like substance on a knife with great success. I have introduced sections of the unexpected-results file to demonstrate how easily DNA can transfer. (Thanks to COVID, everyone now has a far better understanding of droplets in the air.) If you want the analyst to read a study and comment on it, ask for both before they are on the stand. Take notes of your conversation and send them a note asking to confirm they said what you think they said.

Consider the Forensic Evidence in Connection with All Other Evidence

The most obvious example of this is in crime scene photos and police cameras. For example, when police come into contact with a shirtless man, wrestle him to the ground, and cuff him, his DNA is going to be on their hands or gloves. If they later find a gun in the car, they may unwittingly transfer the DNA from their hands or gloves onto the weapon. Or if the police—after arresting the defendant, rifling around in the car, locating a weapon, and placing it on the driver’s seat for pictures—then go and get their gloves, pulling them from the box without a care, and return to the car with their hands wrapped around the gloves, their DNA may transfer to the gloves, and then to the weapon they pick up and deposit in the envelope. (I have seen this more than once.) Many times, the significance of the forensic evidence can be related to how it was handled before it was sent to the lab.


Handling forensic science in the courtroom requires significant preparation. Start early. Review often. Don’t be afraid to ask questions. And good luck.


Christine Funk started her career representing defendants in criminal cases in 1994. After 18 years as a criminal defense attorney in Minnesota, she jumped at the chance to become general counsel for the country's first independent crime lab. After four years in Washington, D.C., She returned to the Twin Cities to develop her criminal practice. She represents defendants facing criminal charges throughout Minnesota.


1  557 U.S. 305 (2009).

2  564 U.S. 647 (2011).

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