What Can Bloodstain-Pattern Analysis Tell us in Minnesota Criminal Cases?

People love criminal forensics. They love watching criminologists in white lab coats on TV and are regularly amazed how they see one drop of blood and they seems to be able to reverse-engineer that single drop to tell exactly what, how and why something happened. Even more, as jurors, this is what they hope to see, even expect to see. This seems especially true for blood and bloodstain-pattern analysis (BPA).  The problem is, this just isn’t true. There are simply limits to what BPA can tell you. If you are facing serious criminal charges in Minnesota and forensics play a role, make sure you sit down with an experienced criminal defense attorney.

What Exactly is Bloodstain-Pattern Analysis?

Blood evidence has become crucial as part of a forensic examination of a crime scene in Minnesota and across the country. The most obvious reason is because of DNA and the ability to generate a DNA profile from the blood found at the scene, if any. This allows investigators to potentially determine identity and more. Sometimes, it is also possible to generate multiple profiles that have the potential to place multiple people at the scene, maybe even a perpetrator and a victim. BPA in one of the sub-categories of forensic science.

Bloodstain-pattern analysis refers to the scientific study of bloodstains and the patterns that they cause. The idea behind this is that the patterns that blood causes when it leaves the body and hits other surfaces may provide additional details about a crime. This may include everything from low-velocity drops, high-impact velocity spatters, swipes and more.  Some 50 years ago, investigators and others started looking at whether it was possible to analyze blood evidence for patterns based upon something called “impact velocity” and how blood behaved with it came into contact with another surface. The general idea was and is to be able to look at different kinds of blood spatter and transfer to be able to answer some basic questions as to what happened at the scene.  What can this simple round drop say?  What can a spatter of fine mist of blood tell us?  What about a swipe on a wall?  Think cast-off patterns, drip patterns and impact patterns.

So What Information Might Blood-Pattern Analysis be able to Provide?

BPA has the ability to provide information as part of a broader forensic examination of a crime scene. With proper training and experience, and depending upon the kinds of evidence provided, there are some things that BPA may be able to help establish including:

• What actions may have created the bloodstain patterns;

• What sequence of actions may have created bloodstain patterns (in other words, what happened first, section and third);

• Possible position of individual when blood deposited, i.e. sitting, standing, etc;

• Potentially general information of weapons used, i.e. knife, other v. guns;

• Number of victims or multiple DNA profiles;

• Potential movement based upon swipe patterns;

• Possible perpetrators if DNA profile;

• Potentially position of victims relative to perpetrators;

• Possible identification of initial location;

• Subsequent tampering with crime scene

What are the Limitations of BloodStain-Pattern Analysis?

While jurors might like to believe that BPA can answer every question in a criminal investigation, BPA cannot do that. In other words, BPA has its limits. BPA simply:

• Cannot recreate the entire scenario

• Cannot determine motivation of the parties

• Cannot determine if the attack was planned or spontaneous

• Cannot determine self defense or defense of others

• Cannot determine if alcohol or drugs made it happen

• Cannot determine initial aggressor

What’s The Problem with Bloodstain Pattern Analysis Anyway?

Accuracy and reliability are critical for any so-called expert to testify with a degree of certainty about what BPA means. The problem is there is no nationwide accreditation or certification and anybody who has more experience than the average person could be called an expert. So “experts” may know what they are doing while others may only sound like it.  Worse, some “experts” will happily testify to all of the things that BPA can tell us but conveniently will leave out all of the limitations. For instance, in a cast-off pattern analysis case, the material the blood hits could dramatically change how blood responds and could easily give an incorrect answer to somebody with insufficient training or who lacks experience. Also, there may be “hired guns” that are brought in by the state. This is how they make their living and there is always a fear that they will say anything for the right price.

So What is Next for Bloodstain Pattern Analysis?

Jurors love BPA and the Minnesota Bureau of Apprehension seems to be continuing to embrace it.  There are continuing efforts to use computer analysis to provide better results.  Of course, the problem with this is: junk in, junk out.  There is always the human factor and trained and experienced humans still have to come up with answers.  The biggest concern, however, continues to be the willingness to conclude that BPA can tell us more than it does. It may be useful but it has its limits.

Go with the Best

If you are facing serious criminal charges in Minnesota and understanding forensics and bloodstain-pattern analysis may be important, make sure that you have an experienced criminal defense attorney. Together you can think these issues through and your attorney may be able to help.

Jack Rice is a Board Certified Criminal Law Specialist, a former Prosecutor, a Former U.S. Federal Officer, and Founder of Jack Rice Defense. If you are facing charges, contact Jack Rice Defense for a free confidential consultation or call 651-447-7650 or 612-227-1339. Jack’s got your back.