Well, who did it?

In the wee hours of August 27, the campus police received a call from a member of the University’s janitorial staff, reporting a break-in on the 3rd floor of Weaver Hall. They arrived to a scene of utter disarray – the normally orderly Organic Lab was a mess, with broken glass, bloody footprints, bullets and bullet casings, tools with possible bloodstains and a tool box labeled “Drug Evidence Locker” that had been broken open, the lock lying next to it on the floor. A white powder was spilled out of a plastic evidence bag and a “bloody” trail led from the box to the rear door of the lab. A crumpled note left on the floor, and the lack of damage to the lab doors, led investigators to believe it had been an “inside” job.

The goal of the Forensic lab team was to collect, process and test the evidence at the crime scene and determine who committed this crime. The police arrested four suspects in the next few days, and evidence was collected from each of the suspects. During the next 14 weeks, the student criminalists processed the evidence. They learned about the properties of soil and glass and tried to characterize the ink present in the crumpled note by Thin Layer Chromatography. There was a shoeprint on the ground outside of Weaver Hall that was found near a discarded 22-caliber weapon, so they learned how to make plaster-of-paris casts of shoeprints. Handwriting analysis, fingerprint analysis, firearms identification and tool-mark casts with “Mikrosil” were done in ensuing weeks. Presumptive blood testing was used to determine if the material strewn throughout the lab was indeed blood, as well as to determine if the stains on the clothing, towels, pants and car were blood. If the stain was blood, ABO blood typing was done. The blood at the crime scene was B-, and so was the blood of two of the suspects. Presumptive drug and alcohol testing was also done, and all four suspects tested “positive” for one drug or another. The student criminalists even used Infrared spectroscopy to identify the drugs. All four suspects also had “adulterated” their urine samples so they clearly were bad apples!

It was an extremely busy semester, and each student criminalist has submitted a final lab report that included descriptions of the evidence, the tests run on the evidence, an analysis of each of the suspects, and a conclusion. For those students who have followed the blog – drum roll please - Stephen Marino is the guy. He was aided and abetted by Julie Alexander, who procured a key and drove him from the scene, bleeding from a wound in his leg caused by a ricochet fragment. Stephen thought he could “choot” the lock off of the drug locker, but was unsuccessful and wounded in the process! He resorted to using wrench and hammer to pry the lock off of the plastic box.

From an instructor perspective (at least this instructor – I will leave Dr. Walker to make her own comments) this course was a very challenging, exciting and incredibly fun experience. We had to stay one step ahead of our student-criminalists and it wasn’t easy! Lab supplies were back-ordered, some tests didn’t work, and we found out that plaster-of-paris makes quite a mess! We were blessed to have attended the Forensic Science Workshop, which gave us the idea to process a crime scene in the first lab, then work on the evidence all semester. It was also very interesting to “create” the crime, and enlist the help of our family members and fellow instructors, who donated articles of clothing that we “bloodied” up. I personally owe a big “thank you” to my nephew and husband, who were more than happy to shoot holes in the “Drug Evidence Locker”, and captured the bullets by shooting through several phone books. Dr. Walker and I had great fun creating the crime scene, although I must say that she went a little crazy squirting the fake blood around the lab. Students – we owe you a big “thank you” for taking this class seriously and working so hard all semester.

Wearing shoes belonging to Dr. Swiger, about to create some footprints!

 

 

It’s all in your genes.

 

Last week, the students had to analyze evidence that is literally invisible to the naked eye…DNA. Perhaps more than any other type of evidence, DNA has changed the world of forensic science by giving investigators a way to link a suspect and a crime scene together beyond the statistical probability of a random match. Traditional fingerprinting is in second place because analyzing the unique number and arrangement of patterns (whorls, loops, arches) can also provide individual characteristics

However, one important advantage of DNA evidence is that it can be collected from almost any cell in the human body, whereas fingerprints must be left by…well, your fingertips. Each cell in your body (other than red blood cells) carries DNA as your genetic material, and it is the specific sequence of how the subunits that make up your DNA determine who you are as an individual. DNA is often referred to as the “language of life” because these subunits of DNA, called nucleotide, instruct your cell on how to assemble proteins, which ultimately determine all of your physical characteristics. The DNA found in the nucleus of your cells is made of about 3 billion nucleotide pairs, and humans in general share over 99% of these pairs in common…that’s what makes us human rather than a grapefruit or a giraffe. It’s this other 1% (or less, usually) that can distinguish us from each other, even from among closely-related individuals. This is DNA’s advantage over blood typing; just because two people have the same blood type doesn’t mean they are related, and it certainly doesn’t mean that two blood samples of the same type came from the same person.

Okay, so back to last week’s lab. A common source of DNA is saliva, which is swimming with epithelial cells from the mouth. Collecting sufficient saliva for DNA extraction isn’t nearly as hard as it used to be, as it’s estimated that DNA can be extracted from as few as 18 epithelial cells. Many of you have seen the CSI’s on TV swab a suspect’s mouth, steal one of his coffee cups, or trick him into using a Kleenex in the interrogation room. The legality of these collection methods isn’t always accurately depicted, but these are realistic sources of human DNA.

In lab Monday, the students tested several pieces of evidence for the presumptive presence of an enzyme called amylase, which is found in human saliva and is important for the first steps of digestion. This enzyme isn’t found in animal saliva, and it’s an uncommon enzyme to be found outside of the human body.

This test is quickly done by swabbing the piece of evidence (cup, envelope, tissue, etc.) that likely carries saliva and transferring the trace evidence to an agar plate that contains starch. Amylase breaks down starch (think digestion) in the plate after only about 10 minutes. After these 10 minutes are up, iodine is added to the plate, which turns the starch black. If amylase is present (and thus saliva, presumably), there will be no starch in the plate for the iodine to reach with. The saliva sample has “cleared” starch from that section of the plate, so you don’t see a color change. In the plate above, the evidence in the top section of the plate is negative for saliva (no amylase activity), whereas the evidence in the bottom section is positive (amylase activity, no starch left).

Once the presence of saliva is identified, further steps will be taken to extract DNA for many forms of analysis. The students got to see just how easy it has become to extract DNA by doing it on their own cheek cells. By using nothing more than salt, dish soap, and cold ethanol, the students extracted their DNA in a tube and then viewed the genetical material under the compound microscope. This in itself doesn’t provide any individual characteristics, as all of our DNA is the same chemically and will look the same in a tube or under a microscope. What would provide individual characteristics is when that DNA is sequenced and compared to DNA found at the crime scene, on the victim, or other on another piece of crime scene evidence.

DNA extraction solution (water, salt, detergent) is added to a person’s saliva or a cheek swab stored in a buffer solution, which break apart human cells so that they release their DNA. Cold ethanol is added to the mixture so that DNA will separate from the cell debris (proteins, carbohydrates, etc.) and precipitate to the bottom of the tube. The ethanol is important for not only separating the DNA from unwanted material but also for purifying it for later procedures. The white material in the bottom of the tube above is concentrated DNA from a human cheek swab. The students didn’t see quite this much DNA in their own tubes, but they did confirm they had collected DNA by viewing the precipitant under the microscope.

This is one of the few times in the semester when I can actually say, “It’s okay if you try this at home…”

Just in time for Halloween…. Blood!

One of the things that I really didn’t want to do in this Forensics class was deal with blood. I have never really liked blood, and one of the reasons I got a doctorate in chemistry rather than go to medical school was that there was much less blood. So why is this post about blood? Because we can’t use real blood in Forensics lab, so we needed fake blood. And guess who whipped up a couple of batches of fake blood in her kitchen?  The chemist!!  Secret Recipe to follow…

Our intrepid students were presented with bloody evidence from our suspects, and also tested blood collected from the crime scene. Their tasks in today’s lab were two-fold – to do “presumptive testing” on the evidence (a pair of jeans, a tee-shirt and a towel) to see if the stains were really blood or paint, or ketchup, and to do blood typing on samples from our suspects as well as samples from the crime scene. The presumptive test that they used is a classic test that you may have seen on TV, the “Kastle-Meyer test”. A sample is smeared on a sterile cotton swab, and a drop or two of ethanol is added to solubilize the blood. A few drops of a solution of phenolphthalin (reduced phenolphthalein) are added, followed by a drop or two of a hydrogen peroxide solution. If the sample contains hemoglobin (i.e. it is blood) the swab turns pink, and the investigator says, in a very serious voice, “It is blood”.

At this time, you may be thinking, didn’t she say that they can’t use real blood? And the answer is “yes”, she did say that. So we had fake blood, and a test for real blood that would not work on the fake blood. I will let you in on a little secret – it is darned difficult to find a “false positive” that will “fool” the Kastle-Meyer test. The literature says that some vegetable extracts (potato, horseradish, cauliflower) have peroxidase enzymes that will give a false positive. They didn’t work very well at all. We actually resorted (at Dr. Walker’s suggestion) to mixing in some ferrous sulfate into the fake blood, but we still had problems in the lab. If anyone reading this has any other ideas, we are open to suggestion!

As a side note, I was delighted to actually make one of the Kastle-Meyer reagents in the lab – the reduced form of phenolphthalein. The reagent that we got from the Kastle-Meyer kit was partially oxidized, and it is best to have freshly prepared. So I got to do chemistry, as well as explain the chemistry of the Kastle-Meyer reaction to the class prior to lab.

Results from the presumptive blood testing. The tee-shirt did not test positive for blood, but the stains on the jeans and towel did test positive for blood. The stains on the floor of the crime scene were also blood.

The blood typing results showed that two of our suspects had the same blood type that was found at the crime scene.

The following photos are of the students performing the “Kastle-Meyer” presumptive test and blood typing using an agglutination test.

Secret Recipe for Fake Blood:  2/3 to 1 cup light corn syrup (i.e. Karo Syrup), 1 – 2 tbsp water, 1 – 2 tbsp corn starch. The corn starch should be added a little at time with vigorous mixing (I used a blender) until the proper “dripping” is achieved. Add about 1 tsp of powdered cocoa and 1 tsp of red food coloring. The cocoa is used to tone down the red food coloring and make the “blood” more rusty-lookng.

The organic lab was a “bloody mess” when I was trying to find a system that would fool the Kastle-Meyer test!

Are you a “high-caliber” criminal investigator?

The students discovered first-hand over the past couple of weeks that firearm and toolmark identification is much more difficult in real life than it is on TV. The forensic specialty of firearm identification focuses on trying to determine the specific firearm from which specific ammunition was discharged. Since many crimes involve one or more guns as a weapon of choice, being able to identify the actual weapon used is of vital importance in linking a suspect with the crime scene.

When examining firearms and their ammunition, investigators first look at class characteristics to narrow down their search. A fairly casual examination by an experienced investigator can provide many helpful clues: the caliber of the weapon, the manufacturer of the ammunition, and the type of weapon used, such as a handgun vs. a rifle. This is only the beginning, though! For example, hundreds of thousands of Glock 9mm semi-automatic pistols have been produced and sold in the U.S. alone, so how can you determine if it’s YOUR SUSPECT’s Glock 9mm that actually did the deed? This is where identifying individual characteristics comes in.

Even two guns that are of the same make and model can have slight differences in their overall structure that make them unique. For example, the barrel of most guns (except shotguns) is actual rifled; it is not smooth. When the bullet travels down the barrel, certain impressions (known as striations) of the barrel’s rifling pattern are left on the surface of the bullet. These striations can be compared to those found on a test, or reference, bullet that is fired from the suspect’s gun. No two guns have the same exact rifling pattern. Keep in mind that at this point, the investigator has a pretty good idea of what type of weapon was used; now he or she is trying to determine the specific weapon used.

Other important individual characteristics include firing pin, extractor, and ejector impressions left on the bullet casing (or jacket) by the weapon’s breechface. Again, even guns that are of the same make and model may have slight imperfections in their breechfaces, leaving a unique impression on every cartridge that is fired from that gun. This individual characteristic is helpful when only the casing of a bullet is found and not the bullet itself. Since the casing itself doesn’t travel down the barrel, it does not acquire any striations on its surface the way the bullet does.

Since a firearm was involved in our crime on campus, the students went about processing the casings and bullet fragments that were collected from the crime scene. Based on a class characteristic analysis, they have determined that a .22 handgun was used to fire the ammunition. They compared the crime scene ammunition to reference ammunition obtained from the guns belonging to some of our suspects. This past week, they had to submit their preliminary report of evidence collected so far, and it will be interesting to read their conclusions concerning which gun (if any of these tested) may have been used…

Dr. Shelly supervises while Kyle and Grace try to reconstruct the path of the bullets that struck the evidence locker. Apparently, the perpetrator tried to shoot the box open, and bullets ricocheted off of the lock and went through parts of the box. Technically, this is “ballistics analysis,” which is different from firearm identification. The field of ballistics attempts to predict or reconstruct the trajectory of bullets fired in order to determine the location of the shooter, victim, and other relevant objects at the crime scene.

Before working with the “real” evidence, the students practiced identifying class characteristics of several reference cartridges, including those fired from handguns, shotguns, and rifles. Here, Cheryl, Seth, and Brandon are using a stereoscopic microscope to examine the firing pin impression left on this handgun ammunition.

After examining the firearm evidence, the students practiced obtaining toolmark impressions from several objects. A toolmark impression is any cut, gouge, dent, or other alteration that is left on one object by another. The term “tool” is a general term for any object that causes this type of impression, although the most common “tools” are pry bars, bolt cutters, screwdrivers, and other objects typically involved in breaking into something. Since it also appears that our perpetrator tried to break into the evidence locker using a hammer and a wrench to bust the lock, determining exactly which tool he or she used is an important aspect of reconstructing the crime scene. A permanent record of the toolmark impression is obtained by using a putty-like substance, such as Mikrosil, to make a malleable cast of the impression. Just like with firearm identification, if a “tool of interest” has been collected, investigators make reference toolmarks with the tool and compare these toolmarks to those left at the crime scene. This way, the tool itself and the object with the toolmarks are not altered or damaged in any way. The important thing to remember is that any trace evidence (hair, fingerprints, paint chips) that may be present should be collected BEFORE Mikrosil is applied; otherwise, you risk losing this precious evidence when you lift the putty from the tool or object. In this picture, Callie and Jessica are comparing the toolmarks left by several Phillips flathead screwdrivers (all made by Craftsmen) and now realize how just knowing the make and model of a tool is, like firearms, not enough to determine what specific tool made the impression.

Stay tuned for the next lab episode, which will likely be very “hairy”…

Evidence and Experimental Results

This gallery contains 8 photos.

Our students have learned that one of the most important things a forensic investigator can do is to capture photos of the crime scene and various pieces of evidence. We have been very busy over the last few weeks, and … Continue reading →

To dust or not to dust: that is the question.

In lab today, our investigators-in-training got to try their hands at a forensic science technique that is very romanticized in many TV shows: dusting for fingerprints. The proper collection of fingerprints at a crime scene and subsequent comparison of those prints to extensive databases of known prints is at the heart of almost any forensic investigation. Fingerprints are crucial in linking a perpetrator to the crime scene because they have both class and individual characteristics. In general, there are three types of ridge patterns that may be found on human fingerprints: arches, whorls, and loops. However, the number and arrangement of these patterns, as well as any other unusual features, make every fingerprint unique to an individual; even identical twins do not share the same fingerprint patterns.

The problem is that most fingerprints left at a crime scene are latent, meaning that they can’t been seen with the naked eye. The ridge patterns are left in an unseen layer of sweat and oil on the object or surface that the perpetrator touched. Finding a visible print, one that is typically found in a layer of dust, blood, or other colored material, is an amazingly lucky break for the average crime scene investigator. Therefore, a fingerprint analyst is one who is not only trained in the comparison of fingerprint patterns but also in locating and collecting them at a crime scene or from an object that has been brought to the crime lab.

Here, Grace and Kyle are practicing their fingerprint dusting skills. In addition to traditional dusting powder, the use of magnetic powder is becoming more popular. Instead of a brush, the magnetic powder is carefully layered over the suspected location of the latent print by a special applicator that gives the investigator incredible control over the amount of powder that is used. Less is better! Regardless of the type of powder used, the rationale behind this method is that the powder adhere to the sweat and oils found in association with the fingerprint. Not touching the print is also critical, as this could smudge the print or alter it in such a way that its authenticity is now questioned.

Drew and Brady are lifting a “practice print” that Travis left purposefully on the lab bench. Once a latent print is dusted and becomes visible, it must be lifted with adhesive tape and attached to an evidence ID card for permanent record. This card will then be scanned into a computer so that a digital image of the fingerprint can be generated, which will be compared to any number of Automated Fingerprint Identification Systems, or AFIS.

Once the students had practiced dusting for and lifting latent fingerprints, they examined some of the evidence left at the crime scene for latent prints that could help them identify the perpetrator. Seth is dusting for latent prints with traditional dusting powder on an evidence locker that was found on the floor at the crime scene and had been shot several times, presumably to break it open. This latent print can be compared to fingerprints of the suspects that the police have apprehended so far in this investigation.

Another important skill of a fingerprint analyst is being to collect a full and good quality set of fingerprints from a suspect for comparative approaches. The students learned that fingerprinting someone isn’t as easy as it looks! After “inking” themselves, the students performed a primary classification of their own fingerprints, which is based on the presence of absence of whorls on fingers that are arranged together in certain pairs and then assigned a mathematical value if a whorl is present. So when is a whorl not a whorl? When it’s a loop, or an arch, or who knows what. The students also learned that classifying fingerprints with the naked eye alone is not for the faint of heart.

The students also continued their shoeprint analysis from last week. Here, Molley, Kyle, and Grace are going over the suspects’ shoes that have been brought in and are making note of their class characteristics, such as size, men’s or women’s, tread pattern, etc. They are still investigating the shoeprints found in the lab crime scene, as well as a shoeprint left in the dirt next to where a discarded handgun was found on campus. Do any of the shoes in custody have a common origin with the shoe(s) that left the crime scene and dirt prints?

Like fingerprints, shoeprints must also be preserved for later analysis. Making a cast of the shoeprint, as Dr. Shelly discussed in her last post, looks easy but rarely is. Several students practiced their shoeprint casting skills last week using Plaster of Paris, and they finally got to see the results in today’s lab. Here, Richterica shows us the cast she made of her own shoeprint left in soil. Now that the students are proficient shoeprint casters, they will soon get the chance to make casts of the suspects’ shoes to see if they can identify any individual characteristics about the shoe(s) that left the prints at the crime scene.

Next up: it seems that the perpetrator tried to shoot the evidence locker in order to break into it, at which he or she apparently succeeded. But what type of weapon was used at the crime scene? Do any of our suspects own such a weapon? Does the weapon found tossed behind a bush on campus appear to be the same one used at the crime scene? Can the bloodied hammer and wrench found at the crime scene help us identify the perpetrator? Find out next week when our CSI’s try their hands at firearm and tool mark analysis!

If the shoe fits…

Note found at the crime scene, written in blue ink.

Today’s lab was chaotic on purpose and very busy! Forensic labs are often overworked (and underpaid, but that’s another story), with evidence trickling in as the police find additional suspects. Our intrepid forensic examiners-in-training rose to the challenge of examining new police reports, cataloging new evidence and re-examining old evidence (crime scene note and photo of the muddy shoeprint). In addition, they practiced handwriting analysis (War Eagle!) and made casts of their own shoeprints using Plaster of Paris and a really neat material called “Biofoam”, AND as if that weren’t enough,  a small dedicated team (Kyle, Molley, Brandon and Cheryl) honed their chromatography skills by analyzing the ink from the note found at the crime scene and comparing it with ink from several pens belonging to the suspects (JA and TH). They found out that chromatography is truly an experimental science, or maybe an art-form! Next week, we will look at the casts of shoes, and the team members that didn’t make the casts will see “if the shoe fits” by seeing if they can match the shoes with the appropriate cast. Note to self: Plaster of Paris in a group setting is extremely messy…  and a heart-felt thanks to Gabe and Michelle for cleaning up.