Posts tagged forensics
Posts tagged forensics
Is it possible to test for cannabis use by sampling a suspected user’s hair, and could you tell if a positive result is due to use or third-hand passive smoking? Research in Drug Testing and Analysis explored condensation of cannabis smoke on hair surface to discover a more accurate method of testing for external contamination. The research analyzed three participants who were exposed to the smoke of one joint every weekday over three weeks.
Traces of 30 hair samples from various regions of the head were obtained up to seven weeks after exposure. The results demonstrated that sidestream cannabis smoke can lead to a considerable and persisting cannabinoid contamination in hair samples.
Read more here http://onlinelibrary.wiley.com/doi/10.1002/dta.1474/abstract;jsessionid=BA3FDE10DBA35097E2F32974CE9425B2.d03t03?systemMessage=Wiley+Online+Library+will+be+disrupted+on+11+May+from+10%3A00-12%3A00+BST+%2805%3A00-07%3A00+EDT%29+for+essential+maintenance
Test fire burn pattern analysis
THIS VIDEO MAY BE GRAPHIC TO SOME. YOU HAVE BEEN WARNED!
Decomposition of a rabbit-time lapse
Blood evidence is a powerful tool for the crime scene investigator. Whether testing for DNA or examining the bloodstain patterns to reconstruct the events of a crime blood is a powerful witness. This fact is not lost on the criminal. This knowledge is rooted in the old saying “caught red-handed” in which a criminal with blood on his hands was thought to be guilty. So criminals have learned to clean crime scenes and evidence and CSIs have learned ways to recover it. Without getting too deep in the forensic weeds; cleaning efforts usually result in either diluting the blood or masking it. Using a washing machine is an effective way of diluting bloodstained clothing. Criminals also have easy access to washing machines so it’s not too surprising that they may utilize them to wash away evidence.
Some of you may already be asking “why not just throw the clothing away?” It’s a good question but to understand it you have to understand a criminal and what they value. A t-shirt may get thrown away like garbage but if the item is their favorite jacket, sports jersey, athletic shoe, or ball cap then they may just roll the dice. One key thing to remember about all criminals. They will clean a crime scene to a point they do not see the evidence. That doesn’t mean the evidence is gone, it’s just beyond the abilities of the criminal to see it. So…will washing clothes destroy blood evidence? Sort of.
I won’t reveal the current state of DNA detection, suffice it to say that researchers are making breakthrough’s all the time. I’ve written before about the durability of DNA evidence and some of the current case studies and research might blow your mind. On the matter of dilution there are some amazing reagents like Luminol that may detect blood at one part per million. Several years ago I conducted a study to see if we could detect bloodstain patterns on washed clothing. I didn’t have high hopes but I thought it may be possible. The long of the short is that a number of cotton shirts were stained with various bloodstain patterns and then subjected to a series of alternating wash and dry cycles. I used washing detergent with bleach and dried the items in a hot-air clothes dryer. The long of the short is that I was able to detect blood on the clothing after five alternating cycles of washing and drying. At the time I used horse blood and DNA testing wasn’t as inexpensive as it is today so I didn’t address that issue. I just wanted to see if the bloodstain patterns could be detected.
The same shirt enhanced with Luminol after five wash/dry cycles. Note the shape of the stains have not changed and even the footwear impression is comparable.
Learning from Skeletons
Look for the sagittal suture – the squiggly line that runs the length of the skull – and note whether is it’s completely fused. If it is, the remains are likely to be of someone older than 35. Look for a second line at the front of the skull — the coronal suture – which fully fuses by age 40.
Study the teeth. If they’re worn down it could be a sign of a poor diet. If they’re well-maintained and/or have good dental work such as fillings, they were able to afford proper dental care—another clue as to the identity of your skeleton. Consult a scientist who specializes in teeth, known as an odontologist. They can determine how old a person was at death, what kind of health they were in and what kind of diet they had.
Examine where the ribs join the sternum. This is also a good indicator of age. A forensic anthropologist will compare it against a database of standard markers and it is often more accurate as it is not a weight-bearing bone and remains unaffected by childbirth.
Look for the pubic symphysis, which is the joint located in the pelvis. The older the person at death, the more pitted and craggy these bones will be. Forensic anthropologists will compare this against a database of standard markers to learn the age of the skeleton. Check if there are any soft marks on the cartilage which are left by childbirth as the bones soften to allow easier birth.
To identify gender, assess the pelvis shape; men have a narrow, deep pelvis and women a wider, shallower pelvis, better-suited to carrying a baby. For a quick identification in the field, a forensic anthropologist will find the notch in the fan-shaped bone of the pelvis and stick their thumb into it. If there’s room to wiggle the thumb, then it’s a female; if it’s a tight fit, it’s the skeleton of a man
Examine the wrists, as bones often hold clues to the primary work of the decedent. Bony ridges form where the muscles were attached and pulled over the years. A forensic anthropologist might find a bony ridge on the wrist and decide the dead person may have been someone who used their hands for a living, such as a chef or seamstress.
DNA samples may be taken from any existing hair tissue. As well as positively identifying someone, it can also identify a person’s race or tribal origins.
When the skeleton is first discovered, take samples from around the remains including any bugs you come across. Insects such as blowflies have a very distinct lifecycle and often plant their eggs on newly deceased bodies. By identifying the stage of the lifecycle, a near-exact time of death can be established. This science is known as forensic entomology.
Ivory Bangle Lady
This series of images showing the skull and how the lady might have looked was created by Aaron Watson of the University of Reading
SICAR®6, is the latest version of Foster & Freeman’s evidence management system, and has been extended to handle tyre marks as well as shoe prints.
Facilities provided by SICAR®6 include:
Identifying shoeprints and tyre tread marks
SICAR®6 adopts a simple coding technique to characterize shoe prints and tyre treads which forms the basis for the database search and match operations. The process, which takes no longer than a minute or two, enables the operator to create a coded description of a pattern by identifying elemental features such as lines, waves, zigzags, circles, diamonds and blocks etc.
SICAR®6 provides information on the frequency of occurrence of a shoe sole or tyre tread pattern at crime scenes and is an estimate of the popularity of shoes or tyres using the pattern. An internal auditing programme also allows you to monitor the use and effectiveness of the system by monitoring key statistics.
Power to link records
SICAR®6 can be used to create links between records, either automatically, as a result of a database search that results in two shoe print or tyre mark records being matched, or manually based on additional intelligence. For example, manual links can be made between the records of a suspect and a known associate or the shoe print records taken from several scenes of crime with a similar modus operandi or different tyre marks found at the crime scene. All links are displayed in a simple ‘tree’ that allows the operator to follow up the associations quickly.
Dealing with partial prints
An image compositor has been added to allow several partial scene-of-crime shoe prints or tyre marks to be joined together to form a more complete image, making visual comparison and matching easier.
If you are ever at a conference and get a chance to talk to the Foster & Freeman guys, do it! SICAR is an AMAZING program!!
Close-up of gasoline spill fire burn pattern on vinyl floor. Photo shows the retreat of the tiles at the intersections
An absence of blood in an otherwise continuous bloodstain or bloodstain pattern.
This pattern was generated by placing a small funnel on top of the target. A fan was then set on medium speed and blood was dropped into the mechanism at an angle that allowed it to strike the target. The funnel was then removed.
It may be possible to determine what object was present during the bloodshed by looking at the void it created after it was removed. It may also be possible to determine the sequence of events by looking at void patterns.
BACK SPATTER OR “BLOWBACK”