forensics

KN, p. 141 “What does a CSI tech really do?”

 

TV makes the job of a CSI tech look like a lot of fun.

 

It looks like an easy job, too. Get a call from dispatch, arrive at a crime scene, pop on the gloves, shine a flashlight around, take a few photos, collect the evidence along with your team of 4-5 colleagues and go back to the lab an hour or so later, ready to process all of it.

 

Have the real CSI techs and law enforcement professionals stopped laughing yet?  😉

Here’s the reality:

 

Most small towns (under 50,000 people) have no CSI lab. None. The local police in smaller towns are able to collect fingerprints, but most have to send them off to a State Lab to be processed.

 

Many towns, even with a population of 100,000 people, don’t have a ballistics lab to check the caliber of any bullets/casings left behind at the scene or found in the victim’s body.

 

North Carolina (as of 2019) had a population of 10.48 million, and has three State crime labs – one full service and two regional labs.

 

New York State (as of 2019) had a population of 19.45 million, and has four State crime labs – one full service and three specializing in varied areas.

 

New Jersey (as of 2019) had a population of 8.88 million.  It has five State labs.

 

Texas (as of 2019) had a population of 28.99 million, with a full service forensic lab in Austin and 14 regional labs, some conducting only drug testing, and others close to full service.

 

And all of those crime labs are processing evidence from all kinds of crimes (burglary, robbery, rape, arson, cold case, assault, etc.) not just murders. It take a few hours to get the prints, preserve the evidence, bag and tag it for transport, but it takes months to get it processed, because there is a long line of cases ahead of yours. In some States, the wait is as long as 18 months. That is not a typo, folks. Eighteen months to wait until the evidence can be processed. Even if the case is a high profile one, moving to the head of the line might only shorten the wait to 2-3 months, because there are other high profile cases in line as well or cases that are already in court, waiting for clarification of the evidence.

 

There is no such thing as instantaneous fingerprint matches. See the article about fingerprint analysis here. There are now handheld machines that scan a viable fingerprint at the scene, but that only speeds up the collection process, not the identification of the fingerprint. (I was recently told that a new fingerprint reader can return an answer in 45 seconds, but some fingerprint experts are reserving judgment as to the accuracy of the matches.)

 

Get the picture? The State Bureaus of Investigation are short-staffed and the cases more numerous, as attorneys seek to prove or disprove beyond the shadow of a doubt that the evidence gathered at the scene linked their clients to the crime.

 

In general, the analysts examine all types of evidence related to criminal investigations and assist the criminal justice system. They can provide:

 

  • Consultation on the value, use, collection, and preservation of evidence,
  • Analysis and comparison of evidence from crime scenes and/or people,
  • Expert testimony in court proceedings, and
  • Assistance for collecting evidence and processing crime scenes,
  • Forensic science information to law enforcement agencies and district attorneys.

 

ALL of that evidence must be collected in a thorough and efficient manner by the Crime Scene Technician or Crime Scene Investigator. Cases are won and lost on how the evidence is handled – both the chain of custody and the collecting of the correct evidence can be factors in how a suspect is perceived.

 

I had a chance to chat with a CSI who has been in the field for about 10 years. She generously shared information about her day – soooo different from the image of the CSI jobs projected on TV.

 

She enters a crime scene after a Patrol Officer has cleared the house (made sure that no unauthorized person is in it). A Deputy might walk her through the house, and depending on the crime, the owner of the house then walks her through, pointing out items that might have been disturbed or areas where items are missing. She takes notes during the tours so that she can come up with a Plan of Action – how to process the scene.

 

In general, she will take photos first, and then collect the evidence. If a homicide is suspected, she might take video as well as still photographs.

 

She might see patterns of wreckage, or concentration of destruction, or even similarities with other cases, but it is not her job to focus on the M.O. (modus operandi) or narrow her collection efforts based on a hunch. She is there to collect all the evidence.

 

She might be looking for:

 

  • Fingerprints
  • Blood spatters
  • Fibers
  • Footwear impressions
  • Tire impressions
  • Tool impressions
  • DNA samples (hair, nails, blood, saliva, etc)
  • Murder weapon
  • Point of entry
  • Kinds of items taken

What a CSI leaves at the scene is sometimes as important as what he/she collects, so it is vital to be thorough. The detectives and attorneys decide what is significant to the case.

 

The trunk of a CSIs car is filled with the tools of the trade. They have kits for each type of evidence collection and if they know in general what the scene will call for, they may grab an additional kit from headquarters. They might even carry a tarp to cover the ground (creating a collection place for the evidence) if the scene is outdoors – such as a train wreck.

 

The CSI I interviewed works in Major Crimes for the Sheriff’s Department, and when she is called to a scene, she works 12-hour shifts, by herself. In most cases, she collects all the evidence, bags and tags it appropriately, and hands it all to the detective in charge. She works 14 days a month, equally divided between the day shift and the night shift.  On occasion, a 12-hour shift is not long enough to collect everything at a particular crime scene, so she stays a bit longer to finish. If it looks as if she has to work for another shift, a Patrol Officer will guard the scene until she returns to finish collection on her next shift. If the case merits 24-hour collection (because of weather or the condition of the scene/body) the CSI on the next shift will continue the collection, with any evidence collected up to that point handed over to the new person.

Clear chain of possession of the evidence dictates that in a case where collection goes on for more than one shift, limited people will have keys to the building. There are evidence cards showing who collected it, and anyone entering or leaving the scene will have to sign in and out with the Patrol Officer on duty.

 

For information about Footwear Evidence, click here.

 

Next week: The life of a CSI – rewards and challenges.

 

 

*Photos taken by Patti Phillips

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FW: “Quick! Grab the glue gun!”


Continuing the series of articles about Evidence Collection Training Classes held at SIRCHIE.

Part 4 – “Quick! Grab the glue gun!”

 

Wet Lift Print as seen on a Comparator

We often hear it said on TV and in the movies that there are items and surfaces that do not hold fingerprints or that fingerprints cannot be recovered from them. On Day #4 of the Sirchie Evidence Collection Training Classes held at the Sirchie Fingerprint Laboratories in NC, we experimented with a variety of surfaces to see what would happen if…

 

Skin is reported to be one of the most difficult surfaces from which to lift a print, because the prints fade so quickly. But, after three days of dusting and chemically treating and lifting and photographing dubious fingerprints, our group of dogged writer/investigators was not to be deterred.

 

The set of prints in the photograph below were lifted from an arm. Not clothing, the arm itself. And not by using fingerprint powder on the arm. A classmate kindly offered up her arm to be grabbed. Then a piece of specially treated paper (chromicoat) was pressed onto the area of her arm where the fingerprints were likely to be found. That paper was then dusted with fingerprint powder and the prints popped up. We now knew it was possible to lift the prints if they were minutes old, but we had access to both the specially treated paper and the powder immediately after the grab. We also knew from experience that our grabber always left really good prints on all the surfaces touched during the previous days.

 

Lift from skin using Chromicoat treated paper

We proposed various scenarios to our instructor (equally curious Robert Skiff, Sirchie Training Manager/Technical Training Specialist). What if a mugger grabbed a bare arm and tried to drag us into an alley? How close would we have to be to the police station after we got away from the mugger in order to get the prints processed? How much time did we have before they faded away? Would the lift work if we used plain paper, since it was highly unlikely that an ordinary gal would be carrying chromicoat paper in a pocket? What if the police station wasn’t close by, therefore no access to fingerprint powder?

 

The answers were time sensitive. It was possible to lift prints from a bare arm with plain paper, but only if the lift was made during the first few minutes and only if the suspect left a strong sample. It’s possible to use cigarette ashes as a substitute for the fingerprint powder. Conclusions? There were too many variables for this to be a reliable way to catch a crook. Now…if you were grabbed around the corner from a police station OR were a smoker AND the mugger had dirty hands AND you had a clean piece of paper in your pocket AND you had attended this class… Hmmm…maybe in a sci-fi mystery. However, not completely impossible.

 

Another difficult surface from which to lift prints is the dashboard of a car. Think about it. If you press your hand onto a dashboard, your skin (with all the loops and whorls and arches) is also pressing into the crevices of the pebbled surface. Same thing is true for an orange or a football. A straight gel lift or hinge lifter will not do the job effectively. A tape lift may only pick up the top of the print.

 

Dashboard surface

 

But, the investigator sees the possible print and doesn’t want to lose the opportunity to catch the crook. The answer in the past was to dust the likely area with magnetic fingerprint powder, then apply a Blue Glue gel and wait for the gel to cure before lifting it off the dash – about five hours. FIVE hours? The crook is getting away! No time to wait!

 

These days, the preferred lifting product (after applying the magnetic powder to enhance the print) is a transparent liquid silicone (PVS200 – polyvinyl siloxane), applied with an extruder gun. It flows down into the crevices, dries in six minutes, and gets into every bit of the print. After the polyvinyl dries, it can be lifted, and then placed on a backing card to preserve the print. At that point, it can be placed under an Optical Comparator, photographed, and sent off to AFIS for an ID/comparison.

 

This epoxy is not good for every surface (it rips paper, etc) but is very good for pitted, bumpy surfaces like alligator skin and dashboards. Gotcha!

 

Dashboard Lift

 

Another tricky scenario: The cop is in pursuit of an unidentified car thief or robber and chases him through a parking lot.  The cop witnesses the suspect firmly planting his palm on the trunk of a car as he cuts through a tight space. The cop grins as he realizes that even if the guy outruns him, he can catch him through the palm print. And, then, it starts to pour. Does the print get washed away? Or become unusable?

 

Not if the Field Kit is handy! When forced to do a wet lift, it is possible to use SPR (Small Particle Reagent – finely ground particles suspended in a detergent solution). Spray the print with a fine mist of SPR and let set. Lay the hinge lifter just off the print and place it down carefully, employing a squeegee at the same time, to slowly remove the excess water. This method can be used to develop prints on non-porous surfaces – cans, bottles, windows, and other glossy surfaces, but not on paper or cardboard.

 

Wet Lift Prints

 

 

Criminals who tie their victims up during the commission of a crime frequently use duct tape for the job. That duct tape is almost always full of prints that get embedded into the tape. It’s practically impossible to manipulate and tear the tape while wearing gloves (I tried this once and the gloves got so stuck to the tape that I threw the resulting mess away), so he leaves prints while unrolling and tearing the tape. Even if he has wiped the smooth surface of the tape clean to cover his identity, the sticky side can’t be wiped without taking away the sticky. Balls of tape tossed aside by a suspect have been processed successfully for prints, but first the tape had to be released from itself.

 

Separating folded duct tape from itself

A 2% chloroform tape release agent is dropped liberally on the area where the two pieces of tape meet. Two people need to work together on this – one person places the drops continuously while the other person pulls the tape apart. The ends of the tape are folded over (about ¼”) and the tape is flattened for 24 hours before further processing.

 

Adhesive-side developer

After 24 hours, adhesive-side developer is applied to the sticky side of the duct tape, allowed to sit for a few minutes, then rinsed off and voila! The prints are clearly visible, can be photographed, covered with clear tape to protect them, viewed under the Optical Comparator, entered into the system, and sent off to AFIS.  (Crystal Violet can also be used for processing this type of print, but is toxic and should only be used in a lab.)

 

Duct tape prints

 

AFIS – what is it and does it really help identify a person of interest in a crime?

 

Anyone who has watched TV crime shows during the last decade has heard the acronym AFIS. It stands for Automated Fingerprint Identification System.  In 1924, the FBI started a fingerprint identification system. They fingerprinted several thousand prisoners incarcerated at Leavenworth, and stored their prints on cards.

 

As of 2012, the system had broadened to include international prints as well, is an electronic database of 70 million, and contains the prints of both law-abiding citizens as well as those of criminals. While newborn babies are printed, their information is usually entered into a local system unless needed in an abduction case. Real estate agents, childcare workers, Federal employees, and people seeking employment with security and law enforcement agencies are fingerprinted as a matter of course now. Depending on the State, the prints are entered into the State AFIS system, and held until needed in the national system. The fingerprints of any person arrested for any level of crime are sent to the State and then on to the national FBI database. The latest FBI version is named IAFIS (I is for Integrated).

 

Johnny Leonard, a latent fingerprint expert, visited the class in the afternoon to explain what AFIS can and can’t do. He showed us what a fingerprint examiner looks for in every print or partial print he/she sees, using the Henry Fingerprint Classification and Identification method. The average number of minutiae on every complete print is between 100 and 150. There are distinct ridge patterns to look for in a print: arches, loops and whorls.

 

Fingerprint Loops

65% of all fingerprint patterns are loops,

 

 

Fingerprint Whorls

30% are whorls,

 

 

Fingerprint Arches

and only 5% of fingerprint patterns are arches.

 

Thumb prints are the prints most often left at a crime scene, because people use their thumbs for leverage when pushing through doors or opening safes, or grabbing those golf clubs to use as weapons, etc.

 

Identifying 8-12 points of similarity between an unknown latent print found at a crime scene and one in the AFIS database is the standard for declaring a match, but some jurisdictions want more for absolute certainty.  An examiner plots the print in question for distinct characteristics, makes notes to that effect before sending the print off and waits. AFIS & IAFIS return a list (sometimes as many as 30) of possible matches. At this point, the examiner reviews the possibles and chooses the best match in his/her opinion. And, it might not be the first on the list. Then, another examiner verifies the possible match. There is no such thing as an instantaneous match with just one print from the AFIS or IAFIS databases. TV tells us otherwise, but sorry, that’s merely for dramatic effect.

 

Other interesting fingerprint details:

*We know that no two people can have the same fingerprints, but not even the same person’s prints are identical.

*Some people have all three types of ridge patterns on one finger.

*Only positive matches from the state AFIS are verified by examiners; not the negative ones.

*Palm prints are now in the AFIS database.

*AFIS looks for change of direction in the whorls, loops, and arches in order to find a match.

*There has not been a case yet where the DNA has not matched the fingerprints at the scene.

 

 

The photo below shows a positive match between a latent print and one in the database. The latent is on the left. The database print is on the right. This match placed the suspect at the scene and along with other evidence, resulted in a conviction.

 

AFIS match

 

Having been through four days of training, working with prints on a variety of surfaces, we felt confident that we were up to the challenge of matching a few fingerprints on our own. Mr. Leonard showed us 16 pairs of prints and gave us 15 minutes to make decisions. We looked for cluster highlights, tented arches, spots, bifurcations and other techy details. Guess what? The lines began to blur, and not all of us correctly identified all the matches.

 

TV makes it look easy, with a click and a less than five-minute response time from IAFIS. Not possible, with 70 million fingerprints to choose from. This is not an easy job, even with the new digital readers that speed up the process of finding likely matches at the scene.

 

Click here for Part 1 – “Have you been fingerprinted?”

Click here for Part 2 – “Where are the Evidence Collection kits made?”

Click here for Part 3 – “Can’t get rid of the blood?”

 

*Photos taken by Patti Phillips at SIRCHIE Education Training Center in Youngsville, NC.

 

FW: “Quick! Grab the glue gun!” Read More »

FW: “Can’t get rid of the blood?”

 

 

Continuing the series of articles about Evidence Collection Training Classes held at SIRCHIE.

Click here for Part 1 – “Have you been fingerprinted?”

Click here for Part 2 – “Where are the Evidence Collection kits made?”

 

Part 3 – “Can’t get rid of the blood?”

 

The morning of Day #3 of Evidence Collection Training classes at the Sirchie Fingerprint Laboratories in Youngsville, NC was spent on the tour of the company’s manufacturing facility. We watched as fiberglass fingerprint brushes were made from start to finish, saw riot helmets being assembled, heard the printing presses rhythmically slap logos and directions onto stacks of waiting cardboard, saw employees counting and rechecking boxes of supplies and chemicals. We witnessed a smoothly running facility. That’s what it takes to insure that the products the law enforcement community uses to catch and prosecute the criminals work. Every time, without fail.

 

After the tour, Robert Skiff (Training Manager/Technical Training Specialist at Sirchie) told us about a new method of fingerprint enhancement developed in Scotland. A bullet can be placed in the middle of an apparatus that shoots electric current into the cartridge and reveals the moisture from a print. This method was demonstrated on an episode of Rizzoli & Isles. Kudos to the show’s writers for including this fascinating technology!

 

Another interesting piece of equipment is the ElectroStatic Dust Print Lifter. Impressions left at a crime scene in the dust on the floor, or on dusty doors or walls, can now be lifted and preserved. A shot of electricity is applied to foil cellophane and any dust below/behind the lifting mat will stick to it. If there is a palm print or fingerprint, it will show up as a mirror image of the original. Rough floors or brick surfaces where a suspect may have jumped, can now be processed using this lifting method.

 

Our afternoon training segment dealt with blood and other bodily fluids.

 

Bloody crime scenes are horrific, but law enforcement officers have to put their feelings aside in order to process and maintain the chain of evidence. Everything they do is aimed at furthering a case to convict, so the scene needs to be secured in order to keep people or animals from contaminating the evidence. If blood is visible at the scene, photographs are taken before the collection process disturbs anything. The photos assist in showing the overall patterns and placement of the drops and splatters. Investigators can determine the approximate place in the room where the victim was first struck, whether the victim was dragged or bludgeoned or shot, if there were one or several victims involved, the velocity of the strike, whether there are arterial spurts, etc.

 

Examples of blood spatter patterns

 

 

 

In order to accurately demonstrate and then analyze the scope and nature of the spatters, the area covered with visible blood is measured and scaled (paper rulers are applied next to the surface being photographed).

 

Blood spatter tagging and scaling

Then it is tagged with information that will help the investigators figure out the sequence of events during the commission of the crime.

Blood Spatter Trail

Specific characteristics of the droplets – whether there is a tail or shaped like an ellipse or a circle, whether small or large circular drops – all reveal information to the investigators and examiners. TV and movie watchers often hear the phrase ‘blunt force trauma’ as a cause of death. This most likely means that the victim has been struck with a baseball bat or a bottle, or a golf club (my fave fictional instrument of death) with medium velocity, so the droplets will be medium sized. (See the drop several inches in front of Mr. Skiff’s finger)

 

A high velocity hit (from a bullet) will have smaller droplets because the blood is broken into smaller pieces as it leaves the body and is sprayed onto the walls or floors.

 

Weapons that are close to the scene or involved in the crime, may get blood on them. They need to be processed for blood as well as prints.

 

Blocking out area of floor of interest to investigator

 

After the visual scans of the room for the visible blood, and the initial photography has been completed, then the areas of possible bloodstains can be swabbed, the samples bagged and identified (as to placement in the room). Presumptive tests can be conducted at the scene, using the Field Kits that contain chemicals commonly used for this purpose. Presumptive tests can help eliminate stains that are not blood, but the stains cannot positively be identified as blood until taken to the lab for confirmation – a detail that TV crime shows frequently fudge.

 

An added level of security for preserving a sample is to make transfers from the original or take chips of the original, but not test the original. That insures that additional tests can be conducted at a later time on the original or pieces of it.

 

 

Unknown Stain

 

 Three transfers were made from an Unknown Stain and then tested with various chemicals.

 

Latent Bloodstain Reagent Products

 

 

 

Unknown stain luminesces

 

 The third transfer was sprayed with a bloodstain reagent, and then the lights were turned off. The Unknown Stain luminesced, therefore indicating the presence of heme, a portion of hemoglobin.

 

If there is no visible blood in the room, but a crime has been reported as having been committed at that site, it is common practice for investigators to work in teams to process the room. The room is darkened, one investigator sprays the walls with a blood search product, while the other marks (tags) the spots that luminesce. The lights are turned on and then the room is photographed, then processed/tested. The method of spraying and tagging is repeated for floors as well.

 

It’s worthwhile to note that blood cannot be destroyed with paint. No matter how many coats, no matter what color paint is covering the evidence of the deed, the tests will always reveal that blood has been spattered beneath it. It gets into every crack and crevice. And it just can’t be washed away. Remember the ‘trace evidence rule’? A crook always leaves something behind.

 

For all you crime show TV junkies out there (I’m one of them): that red blood you see on the bed or wall or floor (hours after a murder has been committed on the show) is strictly for visceral effect. Human blood turns brown or almost black as it dries.

 

 

 

Sexual Assault Collection Kit Record

 

Unfortunately, reports of sexual assault crimes are on the rise. But, ‘He said, she said,’ cases are difficult to prosecute because there are rarely any witnesses to the crimes. Samples taken from the victims need to be pristine and chain of custody must be clearly established. Clothing and bodily fluids need to be collected from the victim as soon as possible after the crime in order to have a chance of catching and prosecuting the perpetrator. A good practice for evidence collection from victims who arrive at the hospital is to have them disrobe while standing in the middle of a sheet. Then the sheet corners can be pulled together, keeping as much evidence as possible intact. Rape victims may not wish to be touched, but swabbing their bodies for fluids, then bagging and testing whatever is collected, may be the only way to tie a suspect to the rape.

 

 

Seminal Fluid Test

A presumptive test can provide important information to include (or exclude) a possible suspect from consideration. There will be an instant (up to 3 seconds) reaction if the unknown substance at the scene or on the victim’s body contains seminal fluid. If the results take longer than that to appear, it must be reported that a false-positive has been found. This might happen if there is not enough of a sample or if the transfer made from the original sample was not good enough.

 

Rape and homicide evidence is kept for years. Bagged, tagged, stored. Photographed and entered in databases as well. If the suspects aren’t caught right away, then the evidence is still there, waiting in storage, to be matched to other evidence that pops up in later crimes.

 

 

*Photos taken by Patti Phillips at SIRCHIE Education Training Center in Youngsville, NC.

 

 

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