Monthly Archives: June 2011
Character Profile: The “Bad” Crime Lab Intern
There are a number of stories about students or trainees (think Silence of the Lambs) that manage to solve a murder. I have had the great pleasure to work with many good student interns over the years. This post is not about them. In terms of character development; an inept, annoying, entitled young crap weasel can really add a lot to your story. I know that sounds harsh but we’re talking fiction right? Bad interns may attempt to camouflage themselves amongst good interns but there are a few details that usually separate the wheat from the chaff.
- The intern is related to some high ranking employee and is “placed” in the lab over students actually pursuing a degree.
- Despite never having investigated a crime they have read “several” text books and regularly point out “mistakes” you are making.
- Upon hearing that they will not be allowed to actually participate in collecting evidence at a homicide scene they initiate a formal complaint.
- No matter how bad they are you simply can’t get rid of them.
- They have “expertise” in things like reading tea leaves, Oujie boards, and the magic 8 ball.
- They “speak” to the dead.
Alright, maybe I’m exaggerating a little (on 5 & 6) but you get the point. In a way, a bad intern is like that annoying family member you have to invite to family dinners. The good news is that this character provides a lot of possibilities. You could have an intern who tries to collect evidence (but does it incorrectly) at a major scene. They might leak information to the press, jeopardizing the investigation because they feel under appreciated .
If you’re writing a courtroom thriller you could have an intern who thinks they know a lot but are taken to task by a good defense attorney derailing a case. Another thought is to have an intern who is a former gang member or sympathetic to a gang. Alternatively, they could be threatened by a gang to infiltrate the evidence section and either plant evidence or compromise it. Most interns must undergo a criminal background check but if they have no arrest record they won’t raise any red flags (in theory).
In any event, have some fun with it and see if this character can bring your story some comic relief or high stakes adrenalin.
Silvia Pettem: How One Woman Made a Difference
Dorothy Gay Howard - Murdered April 1954
Local historian Silvia Pettem is not what one might imagine when you hear the word “detective” but I contend she is a force to be reckoned with. Were it not for her hard work and tenacity a young murdered woman may have never been identified. Her name was Dorothy Gay Howard. She laid in an Boulder, Colorado grave yard with a headstone bearing the name “Jane Doe” and the story of Siliva’s quest to identify her is inspiring.
What makes the sotry inspiring is that Silvia is not a police detective. She is a local historian and concerned citizen who decided to make a difference. She used her impressive skills to track down historic information and lost files that were all but lost to time. Time can be a detective’s nemesis. Information is created by people and people have an expiration date (dark, I know). Even before death many people have a “best when used by” date as far as memory goes.
Good historians, like Silvia, are experts in finding information from non-traditional sources the police have come to reply upon. I’m not writing this post as purely praise for Silvia. But I hope that when you are considering character development you consider some non-traditional “detectives” that may be able to uncover facts and provide important perspectives to the police. Archaeologists, historians, psychologists, non-forensic scientists, etc. can have tremendous insight to certain aspects of a case.
Police are sometimes reluctant to solicit the help of “civilians”, especially in open homicide investigations. Let’s face it, some case evidence needs to be kept close to the vest by people who are accountable to the agency. On the flip side, law enforcement can benefit greatly by enlisting the assistance of those experts who have proven themselves to be both competent and professional. The trick is figuring out who is a valuable source and who isn’t.
Skeletonization: An Artifact of Blood Drying
Blood droplet drying. See the outer ring changing color?
Bloodstains dry from the outer perimeter to the center. Not exactly page turning information but this process can lead to an artifact known as skeletonization. You see, once blood is deposited and begins drying, any disturbance to that blood will affect the “wet” portion in the middle but leave the outer dried ring undisturbed. The longer the drying time the thicker the drying ring (see images below). Bloodstain pattern analysts can use this evidence to calculate how much time passed between the initial deposition and the subsequent disturbance.
This drying process can be influenced by a number of factors. Temperature is one consideration. The hotter the temperature the more quickly it will dry. Not just air temperature either. The temperature of the surface the blood is on will affect drying time as well. Blood volume is another consideration. A small droplet will dry faster than a pool of blood.
So what does this mean for you? There are ways you (i.e. your characters) can use this information to shed light on a crime. More specifically the timing of certain events. This may be especially important in staged crime scenes. Imagine a jealous ex-boyfriend who sneaks into his old girlfriend’s bedroom. When she gets home an argument ensues and leads to an assault ending in murder. During that initial assault the victim bleeds a few drops on the floor. After killing the victim the suspect panics and decides to stage the death as a burglary gone wrong. He drags the victim down the hall to another location but in doing so her legs smear the drying blood drops.
By looking at those drops an analyst might be able to tell that, say, ten minutes passed between the depositing of the blood and the dragging of the body. Criminalists obviously want to explain why there is a delay (like staging a scene). Sometimes the skeletonized patterns can be found after they are cleaned up. These stains are found through the use of blood reagents like Luminol. These stains are also very helpful in sequencing events.
Skeletonized blood droplet after five minutes
Skeletonized droplet after ten minutes
Skeletonized droplet after fifteen minutes
Forensic “Controls”
The O.J. Simpson trial brought the idea of forensic “controls” into the public lexicon. Since then the term has been sprinkled here and there in the literature and television. I thought it might help to define the term and give you some examples should you choose to put it in your novel. A control is a sample that serves to represent a source. Clear as mud right? There are two basic types of controls; evidentiary and testing. I’ll provide some examples of these as well as why forensic scientists collect them in the hopes that their purpose becomes clear.
Test of Phenolphthalein on diluted blood as "Control"
An evidence control is a sample that can be analyzed independently of “other” evidence collected in proximity. For example, when an analyst swabs a blood droplet from a counter with the intent of testing it for DNA there is a presumption that the resulting DNA profile is from the blood right? But…what if someone makes the argument that the DNA was already there on the counter when the blood droplet got there? Maybe the contributor sneezed on the counter 20 minutes before the blood was deposited. If the analyst swabs an adjacent area of the counter top not containing blood then they have a “control” that will give them information about the background. Obviously, when the blood is finally tested there should be evidence of multiple donors and if not we can say the subsurface was “free” of recoverable DNA (in theory). But you wouldn’t know that at the crime scene so collecting a control sample is one way to address this issue at the time of collection.
A testing control is a sample that is used to evaluate the reactivity of a particular test. For example, if the criminalist wants to use a blood reagent like Luminol to search for blood, they would want to make sure the chemistry is working correctly before they start correct? In order to “test” the reliability of a reagent (for example) you have to have a known sample (i.e. blood) to try it out on. To accomplish this, the criminalist may have a reaction card with them. A reaction card is a testable surface (like blotter paper or cotton swatch) containing a known sample (like blood). I used my own blood so that if any accusations of cross-contamination were made I knew the source of the sample (me) to test. So after mixing the chemistry I could test it on the sample swatch (outside of and away from the crime scene) to be sure the chemistry was working correctly. Similar testing can be done with an ALS or even classes of evidence like drugs.
So how can you use this in a story? Well, what if your character doesn’t take a control and then there is a question about whether or not the DNA sample came from the blood? If there is a mixed sample in the blood DNA did it come from the surface or from another donor (alternate suspect)? What happens if the chemical reagents they use are n;’t working correctly? What if an intern mixed the chemistry and forgot an important component? Your character sprays the chemistry with no results and declares “Nope…no blood here”. Then later on maybe someone else uses the same reagent and gets a positive reaction. That could set up some real dilemmas in your story. Remember, forensics isn’t just about finding evidence. It’s also about making sense of the evidence we find.
What is a “Known Standard”?
Crime scene investigators collect all types of evidence that, when compared to a source, may provide powerful associations between the suspect, victim, and/or crime scene. These standards may be used to associate that evidence by either class or individual characteristics. Crime scene samples are sometimes referred to as “question” samples because we don’t know from what source it originated. The analyst may label these items as “Q1″, “Q2″, “Q3″, etc. This can include latent fingerprints, shoe impressions, bloodstain samples, fired bullets or cartridge cases, and a variety of trace evidence. But in and of themselves they may not have the weight necessary for a prosecution. Prosecutors are required to obtain a high level of proof before taking a case to trial. This is where the known standard comes in.
Applying fingerprint powder to outsole to make a transparency
A known standard is an item or sample of evidence from a verifiable source. Known samples are sometimes labeled as “K1″, “K2″, “K3″, etc. This may be the inked fingerprints we get from a suspect, their shoes used for comparison (from their possession), a sample of their blood (drawn from their body), bullets and cartridge casings fired from a specific weapon in the possession of the examiner, a handwriting sample from the suspect, etc. These types of sources may individualize that questioned sample with the known sample. That means that in the examiner’s opinion the evidence is associated with that source and no other. It is the most powerful type of association. Other types of evidence like soil samples from the suspect’s home or crime scene, fiber samples from the victim’s carpet, glass fragments, etc. may simply associate that evidence by class characteristics. It may still be a compelling association but does not link to a specific source.
I bring this topic up because writer’s should be aware of what components are required to make the associations we so often see in story lines. It sounds great when a detective says “Hey, look here, the suspect had this red colored soil on his shoes”. That’s fine but there has to be an expert analysis too. So if you’re going to introduce class evidence like soil, try to associate it with some location that has some rare or unique qualities to it. Maybe it’s red soil that also contains a rare mineral or pollen that is only found in one location (dump site). You can get pretty creative with it and still sound reasonable.
With individualized evidence you may want to have a character surmise the type of known standard from the crime scene evidence. For example, maybe you have an unusual cartridge case like a .44 rimfire that significantly reduces the number of possible known standards (rare antique firearms) that could have fired it. You might also have a shoe tread pattern that is from a shoe sold only in a foreign country. Again, the information gained initially is only class oriented until the detectives recover the known source but it can make for some interesting plot twists. Something to think about.
What is “Match Analysis”?
Broken plastic from a vehicle accident
When items are “broken” they form unique edges. The manner in which an item breaks is random because the force and direction of force applied is random. Because these edges are formed randomly they may be considered individual characteristics (depending on how well defined the edges are). Whether it’s a traffic accident, assault, vandalism, or homicide if certain broken pieces are left behind by the suspect at the crime scene then the potential exists to link that suspect to the crime by their possession of the matching broken pieces. You’ve all probably read stories about hit and run accidents wherein parts of the suspect vehicle were left behind at the accident scene. If you’re really lucky you’ll find a bumper with the license plate still attached but usually it’s broken pieces of light housings or paint fragments. The same type of analysis can be done in any crime where items are broken. The critical aspect is that the broken pieces retain defined edges that can be compared to one another.
I have a simple experiment for you to try. Take a photograph or written document and make 5-10 photocopies of it. Working with only one sheet of paper at a time then do the following. Tear the page in half. Put the two halves together (doesn’t need to be aligned) and tear them in half again making four pieces. On the back of each piece write the numeral ”1″. Repeat the process, one page at a time, labeling each group sequentially (second page is group “2″, third sheet is group “3″, etc.). Take the four pages from group 1 and put them back together so the tears align. See how the edges of the tears fit together. Look closely at the images or words on the document and exactly where they are torn apart. Then assemble each group on the floor or a table so all of the assembled groups are in front of you (you’ll be looking at 5-10 identical documents).
Broken plastic pieces fit back together
Now comes the interesting part. Take a piece from group 1 and see if you can make it fit into the corresponding area of any of the other documents. Then try another section. Can any of the torn pieces be “fit” convincingly into any of the other identical documents? The answer is no. Congratulations, you’ve just performed your first “match analysis”. In your story line you may have a scene where a suspect beats a victim with a pool cue that breaks in half. He leaves the tip at the scene and dumps the other end in his car. Or maybe you have two people fighting over a document which tears in half.
Actually, when I used to collect carpet samples of bloodstains I would cut them out in different geometric shapes and photograph the spots they were taken from afterwards. That way, if there became a question later in court about the location it was collected from, that particular shaped sample could only “fit” back into one (and in one orientation) location in the crime scene. Same principle, just a different purpose.
The Forensic Response to Abducted Children Part I: An Overview
Nothing can stir up emotions like a missing child. Children, unlike adults, are universally viewed as vulnerable and innocent by most people. When a child goes missing there is an instinctive response to panic and rush out to find them. In reality, these cases deserve deliberate well reasoned responses. That’s not to say that police don’t take them seriously. It’s appropriate for officers, volunteers, and the public to start searching every shadow. This series of articles will focus on the response by the forensic scientist. Our response is usually very different than that of the patrol officer. That’s because we have different roles in the process.
Primarily I will be discussing stranger abductions as opposed to parental kidnappings. Parental kidnappings are crimes too but law enforcement generally has a lot more to go on in these cases. As in any crime, there is a crime scene, a suspect or suspects, and a victim. The primary crime scene is the abduction site but secondary scenes such as vehicles, residences, incidental or transition sites (like a restaurant) and possibly a murder site are other possibilities. At these locations the CSI will search for evidence of both the suspect and the victim.
When considering the suspect we hope to find evidence that will identify that person to law enforcement. This may include fingerprints, DNA, surveillance images, a license plate, etc. Other information like clothing descriptions and vehicle descriptions may also aid searchers in finding them. Several possible motives exist in stranger abductions which can be influenced by the age of the victim. Infants may be taken because the abductor can’t have children of their own or believe the child may be in an unhealthy environment. Usually there is some degree of mental illness or depression on the part of the abductor. Adolescents may be targeted by pedophiles who may or may not ultimately murder their victims. Most stranger abductors are white males under 30 but realistically they may inhabit any number of demographics.
If you plan on writing about a child abduction you would do well to put some thought into the motives of your suspect(s) as well at the location they choose to commit their crime. That is if it doesn’t creep you out too much. Do they try to abduct the child from a public environment like a park, playground, or route home from school? Or do they select their home? How did they first target the victim? How do they know where the victim lives? Why did they choose the home rather than a public setting? These are many of the questions the CSI will ask in order to formulate our response. Keep checking back over the next few weeks for additional postings on this topic.
Bloodstain Pattern Analysis 101: Basic Properties of Blood
Bloodstained Knife
Blood is a fascinating liquid to study in relation to forensics. About 55% of blood is plasma. Plasma is the “liquid” component made up of proteins, salts, acids, and water. Actually a little over 90% of plasma is water. The other 45% of blood is made up of the cellular material (often called the “formed elements”). There are three types of blood cells; red, white, and platelets. The majority are red blood cells. Interestingly, red blood cells contain no nuclei and therefore have no value for DNA testing. In fact, when you consider all properties of blood (plasma and cells) only 1% of that material contains DNA; and that material is randomly distributed throughout the blood volume.
Blood is about 4-5 times more viscous (thicker) than water. Another interesting quality of blood is that it is somewhat adhesive. You might be thinking “so what?” but there is a reason these characteristics are important to bloodstain analysts. Thick, sticky blood means that it will adhere to other objects. Those objects may transfer a blood pattern to another object. The more this happens, the more we have to analyze. A suspect with blood on his/her hands may leave bloody finger or palm prints at the crime scene. Blood on their shirt may transfer to the seat of the getaway car. Blood on their shoes may seep into seams and remain there for months. Even if the blood is cleaned up, trace amounts may still exist.
Bloody transfer of ring on T-shirt
If you are writing a homicide scene, you may want to consider how any blood on your suspect might be transferred during or after the crime. If they transport a victim in their car will blood leak out onto the floorboards or into the trunk? If the victim is wrapped in something, what will the killer do with those bloodstained wrappings? In that disposal will any of the blood transfer to the suspect, vehicle, or other objects? As long as blood is somewhat “wet” it can transfer to other objects. Remember, even “invisible” trace amounts of blood can be valuable to the forensic analyst.
How Criminalists “Touch” Evidence
This information might be better suited for a screenplay but I think you’ll find some value in it for novels as well. Forensics is about observation. Good forensics is understanding what you’ve observed. Try an experiment I’ve asked a number of interns to complete. Over the next few weeks watch how people handle certain objects. To simplify things you can watch for a certain activity (like opening doors) each day. How do people enter through a door? Do they grab the handle going in? What about coming out? If they hold the door open, where do they grab it? Don’t just look at buildings, watch people getting in and out of vehicles too.
The next day watch how people hold a glass or bottle while drinking from it. Do they grab it in approximately the same place each time? Do they clasp it with all of their fingers or just a few? The watch people reading a book, reading a piece of paper, or looking at a photograph. It may sound kind of goofy but as criminalists we want to understand how people handle things because that tells us where we expect to find fingerprints. More importantly, it tells us where not to touch. This only applies to smooth areas that can hold a fingerprint in the first place. If the area is textured (like the grips of some pistols) or if it is very small like the tab on a beer can we can safely assume no comparable fingerprint is there.
Notice how I handle the beer can by the tab while dusting for fingerprints
Think about it. If we handle objects in the same manner that the average person does then we run a greater risk of smudging the very evidence we’re searching for. That’s the last thing we want. For example, if I’m entering a crime scene (say a bank) through the door I’m not going to just grab the handle and yank it open. If I have to grab the handle I’ll grab the top corner or edge of the handle to get the door open a bit and then I may grab near the top of the frame to open it all the way. We never want to touch where the suspect likely touched.
After you’ve spent a week or so watching how people handle objects ask yourself how you’d do the same activity without touching the same areas they did. Many times we have to handle objects by the edges or by any area too small to hold a fingerprint. It makes our job a little more challenging sometimes but the reward can break a case wide open.
Oblique Lighting Explained
Shoe print seen with oblique lighting
Have you ever noticed how the CSIs on television seem to examine everything with a flashlight instead of turning on the lights? It drives my wife nuts! Eventually we do turn on the lights but in some scenes it actually helps to look around with a flashlight first. That’s because some items of evidence are easier to see with oblique lighting (also known as side or indirect lighting). Overhead lights don’t create the harsh shadows needed to see certain evidence. Simply stated, the CSI will take a bright flashlight and hold it at a very low angle parallel to the surface they are examining (like a floor). The process works best when all other lights are turned off. You can try this yourself at home. You’ll be amazed at how much dust, pet hair, and other small items you’ll see using this simple technique.
Below are photos of a wooden stool that was found at a crime scene. Looking at the stool in room light no one saw the two sets of shoe impressions from the suspects. They had used the stool to gain access to an otherwise inaccessible area in the crime scene. Without oblique lighting this valuable evidence would probably never have been found. If you want to use this in a book scene you could have your CSI, detective, or private eye find evidence after others have released the crime scene. In any event, don’t be shy about having your characters using flashlights in a crime scene, even during daylight hours.
Stool seen in normal lighting
Shoe prints on stool seen with oblique lighting
