For ten long years, David Foran, a molecular geneticist and forensic scientist at Michigan State University, has worked to turn the bacteria found in soil into permissible evidence in criminal cases. It was a former student, though, a microbiology major, who first came up with the idea.

This could be an earth-shattering breakthrough since the goal of the research is to establish an objective standard, backed by solid statistical data, that could link soil found on a particular item to soil from a crime crime. The technique uses the DNA of bacteria from a sample, say on a digging implement—shovel, pick, spade, etc., to that found in soil from the scene of the crime. Of course, numerous factors could alter/influence each sample—temperature, foreign substances such as blood, sweat, chemicals, etc.—and each of those would be studied, classified, and categorized to allow for inclusion or exclusion (sample matches a known soil and substance, or not).

Once the research is perfected courts may then allow the testing method and soon after crime labs would then add it to their crime-solving toolboxes.

Daubert, Frye, and Using Bacteria Found in Soil to Solve Criminal Cases

So how does a procedure become suitable for courtroom and legal proceedings? What are the rules regarding who may testify as an expert witness?

Narcotics investigations

I was once put through the ringer in a courtroom before being declared, by a superior court judge, as an expert witness on narcotics and how they’re made, packaged, and sold.

This was during a time when my major focus as an investigator was on major drug cases.

Typically, judges make the final decision as to who or what is allowed in their courtrooms, and that includes which evidence is admissible and who may or may not testify as an expert witness. And, they normally rely on either the Daubert standard or Frye, both precedent setting case. Some states follow Daubert. Others follow Frye. And a small handful use either.

Daubert v. Merrell Dow Pharmaceuticals 


Frye v. United States, 293 F. 1013 (D.C. Cir. 1923)


Daubert is by far the most widely used standard in courtrooms across the country, and the rules according to Daubert are:

Per Cornell Law School ( – “Standard used by a trial judge to make a preliminary assessment of whether an expert’s scientific testimony is based on reasoning or methodology that is scientifically valid and can properly be applied to the facts at issue. Under this standard, the factors that may be considered in determining whether the methodology is valid are: (1) whether the theory or technique in question can be and has been tested; (2) whether it has been subjected to peer review and publication; (3) its known or potential error rate; (4) the existence and maintenance of standards controlling its operation; and (5) whether it has attracted widespread acceptance within a relevant scientific community. See Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579 (1993). The Daubert standard is the test currently used in the federal courts and some state courts.  In the federal courts, it replaced the Frye standard.”

Now, back to the soil sampling. Here’s a nugget for your research files. I once investigated a murder where I collected soil samples, among many, many other pieces of evidence, hoping to find the needle in the haystack. Without a bit of good luck this case could’ve quickly gone cold.

Fortunately, scientists matched a single, unusual plant seed I found and collected at the crime scene to one found in dried mud stuck to the accelerator pedal of the killer’s car (I also collected this sample). The plant grew in only one location in the area, at a particular spot near a river—the very spot where the body was found. I had a hunch and it paid off.

That one tiny seed was the icing on the cake in this case. I also matched tire tracks and I eventually obtained a confession from the suspect.

Here are the details of the sad case case (above) told in a brief writeup you might find interesting. A Dead Woman Crying: Murder in the Rain.

During their crime-solving duties homicide investigators hear a lot of details, sounds of gunfire and people running, bits of spoken evidence, and much more. But one thing they’d best pay particular attention to is what the body has to say, and believe me, it’s usually a lot.

Dead bodies always have a lot to reveal to investigators!

Putrefaction is the destruction of the soft tissue caused by two things, bacteria and enzymes. As the bacteria and enzymes do their jobs the body immediately begins to discolor and transform into liquids and gases. The odd thing about the bacteria that destroys tissue at death is that much of it has been living in the respiratory and intestinal tracts all along.  Of course, if the deceased had contracted a bacterial infection prior to death, that bacteria, such as septicemia (blood poisoning), would aid in increasing the body’s decomposition.

Temperature plays an important part in decomposition. 70 degrees to 100 degrees F is the optimal range for bacteria and enzymes to do what they do best, while lower temperatures slow the process. Therefore, and obviously, a body will decompose faster during the sweltering days of summertime.


A blood-filled circulatory system acts as a super-highway for those organisms that destroy the body after death. Without blood the process of putrefaction is slowed.

Therefore, a murder victim whose body bled out will decompose at a slower rate than someone who died of natural causes.

Bodies adorned in thick, heavy clothing (the material retains heat) decompose more rapidly than the norm. Electric blankets also speed up decomposition.

A body will decompose faster during the sweltering days of summertime.

A body that’s buried in warm soil may decompose faster than one that’s buried during the dead of winter. The type of soil that surrounds the body also has an effect on the rate of decomposition. For example, the soil in North Carolina is normally a reddish type of clay. The density of that clay can greatly retard the decomposition process because it reduces the circulation of air that’s found in a less dense, more sandy-type of earth.

Adult bodies buried in a well drained soil will become skeletonized in approximately 10 years. A child’s body in about five years.

People who were overweight at the time of their deaths decompose faster than skinny people. People who suffered from excessive fluid build-up decompose faster than those who were dehydrated. And people with massive infections and congestive heart failure will also decompose at a more rapid rate than those without those conditions.

The rule of thumb for the decomposition of a body is that, at the same temperature, 8 weeks in well-drained soil equals two weeks in the water, or one week exposed to the air.

Now, hold on to your breakfast …

The first sign of decomposition under average conditions is a greenish discoloration of the skin at the abdomen. This is apparent at 36-72 hours.

Next – Small vessels in the skin become visible (marbling).

Followed by, glistening skin, skin slippage, purplish skin, blisters, distended abdomen (after one week – caused by gases), blood-stained fluid oozing from body openings (nose, mouth, etc.), swelling of tissue and the presence of foul gaseous odor, greenish-purple face, swollen eyelids and pouting lips, swollen face, protruding tongue, hair pulls out easily, fingernails come off easily, skin from hands pulls off (gloving), body swells and appears greatly obese.

Internally, the body is decomposing and breaking down. The heart has become flabby and soft. The liver has honeycombed, and the kidneys are like wet sponges. The brain is nearly liquid, and the lungs may be a bit brittle.

Wrong kind of brittle, but who wants to end the post with crunchy lungs? So have some homemade peanut brittle and enjoy your day.