Category Archives: Blood Analysis

Q and A: How Could My Character Keep Blood In a Liquid State For Later Consumption?

Q: I have a killer who drinks the blood of his victims. If he wants to bleed out a victim and wind up with blood in his freezer that he can reheat in a Mr. Coffee, I assume he’ll need some sort of anticoagulant. Is that right? Would he have to use it immediately at the murder scene? What would the average person have access to that could serve this purpose, especially if he didn’t preplan his first kill. Better still, is there some way to reconstitute the blood after it coagulates?

Craig Faustus Buck, Sherman Oaks CA


LEFT: Clotted and Separated Blood RIGHT: Unclotted Blood

LEFT: Clotted and Separated Blood
RIGHT: Unclotted Blood


A: Actually there are several ways to accomplish this. If your killer has access to the victim for several days or weeks prior to the event, he could slip some Coumadin into his food daily for two or three weeks prior to the killing. Coumadin, or warfarin, is an oral anticoagulant that works mostly in the liver to prevent blood clotting. It takes a week or so to build up to levels that would keep the blood liquid.

That might be cumbersome for your story, so there is another choice. Heparin. Heparin should be given intravenously but it works immediately as an anticoagulant. Your killer could inject a large dose of heparin right before the killing. This would of course require that he have full control of the victim or at least convince the victim that the injection was harmless. Either way, if he gave 100,000 to 200,000 units of heparin intravenously the victim’s blood would be anti-coagulated within seconds and he could then bleed him and store the blood as a liquid for an extended period of time.

Lastly, as he drained the blood he could put it into a container that contained EDTA. This is what is used in the blood vials when blood is drawn that needs to be anti-coagulated for certain tests. It’s a white powder that is available from pharmaceutical supply houses. Mixing some of this with the blood would prevent it from coagulating so it could be stored as a liquid.

As far a reconstituting it, once blood clots it immediately begins to separate into the reddish clot and the yellowish serum. Vigorous shaking or running it through a blender could remix the blood, resulting in a red liquid that he could then consume.


Posted by on July 18, 2014 in Blood Analysis, Medical Issues, Q&A


Do Identical Twins Have Different DNA?



DNA profiling is considered the gold standard for individual identification. DNA-containing bodily fluids found at crime scenes can often be linked to the perpetrator with a high degree of accuracy, often measured in one per billions. It is highly individual and therefore highly accurate for identifying a given individual.

But since identical twins begin as the same fertilized egg, they have identical genetic material (DNA). After fertilization, the fertilized egg divides into two cells. To produce identical twins, these two cells separate and then each progresses forward to produce an individual. This results in two identical individuals with identical DNA. Or does it?

Twins egg:sperm


Standard DNA testing uses the concept of Short Tandem Repeats (STR’s). STR’s are simply short segments of DNA that repeat in certain areas of the very long DNA strand found in all of us. The number of these repeats in the various locations are what allow DNA profiling to distinguish individuals so accurately. This is a complex, though not really difficult to understand, technique which is discussed in great detail in two of my books: Forensics For Dummies and Howdunnit: Forensics.

DNA Profile

But scientists have known for years that the DNA of identical twins is not perfectly identical. It might or might not start out that way at that first cell division but for sure as the cells divide and the individual grows within the uterus, minor DNA changes can occur. These are on the level of the base pair sequences that make up the DNA chain.

Another DNA technique called Single Nucleotide Polymorphism (SNP) actually looks at each base in the DNA strand and uses this for comparison with another strand to determine if they came from the same individual. This is the direction that DNA testing is going but for now STR remains the method of choice.

Identical twins would look the same using STR analysis but a deeper analysis using SNP would reveal variations, thus allowing identification and separation of two identical twins. Let’s say, blood is left at a crime scene and that blood is matched to a particular individual. Let’s further say that this individual is an identical twin. STR DNA analysis would not distinguish between these two brothers, But if SNP is employed, the one who left the blood at the scene can be distinguished from his identical twin.

The recent French serial rape investigation involving identical twins Yohan and Elwin would be a case in point. Applying the SNP technique in this situation would likely solve the case.

Pretty cool stuff.

Howdunnit Forensics Cover




Single nucleotide polymorphism (SNP) is a new technique that will likely see increased use in the future. The major problem at present is that it is expensive. We saw that RFLP fragments were fairly long, a drawback that lessens their value in degraded or damaged samples (discussed later). This problem was circumvented by the discovery of STRs, which are very short fragments. But, what if the DNA examiner could use single nucleotide bases as the standard for matching? This would increase the discriminatory power of DNA even further. This is what SNP does.

Let’s say that two sequenced DNA strands looked like this:


If we searched for an “ATTA” STR repeat, these two strands would be indistinguishable

since both have two ATTA repeats. But, with single nucleotide analysis the strands differ by a single base: The ninth base in the first sequence is guanine (G), while it is adenine (A) in the second one. SNP can be used with restriction enzymes in the RFLP technique, or with PCR, where it can be easily automated. Theoretically, this will allow for discriminating two DNA samples based on a single nucleotide difference.


Bloodstain Camera Finds Blood Quickly and Efficiently

Detecting blood at a crime scene is often essential for determining if a crime did indeed occur and how the act unfolded—crime scene reconstruction. At the scene, a meticulous search for blood can be tedious, time-consuming, and eat up many man-hours.


Techs search for bloodstains

Techs search for bloodstains


Shed blood is not always obvious. The stains are not always patent (visible) but rather latent (invisible). The standard in such situations has been to employ Luminol, which can find even very small latent bloodstains. But Luminol takes time and requires darkness—not always obtainable, particularly in outdoor, daytime crime scenes.


Luminol helps expose latent bloody shoeprints

Luminol helps expose latent bloody shoeprints


A new technology developed by Dr. Meez Islam and colleagues at Teeside University promises to not only be able to detect latent blood spatters quickly but also age the blood very accurately. With month-old stains the device, which uses hyperspectral imaging, can narrow its deposition down to a day and with fresh blood down to an hour. This should greatly help with Time of Death determination—-or at least the time when the blood was shed.


Fresh blood spatter

Fresh blood spatter


Blood exits the body bright red but with time and oxidation becomes rusty brown and does so along a predictable timeline. Accurate determination of the bloodstain’s color with hyperspectral imaging reveals its approximate age.

Very cool. And potentially very useful.


Q and A: Could My Young Roman Girl Estimate the Time a Death Occurred From the Blood at the Scene?

Q: I’m writing a young-adult novel set in the ancient Roman world. My “detective” is a slave girl without medical training but who has lived on a farm and observed animals being butchered. I need her to be suspicious about the reported time of death of a woman, based on the state of the body and the condition of the blood (the woman’s throat was cut and blood is still dripping off her bed when she is found). What would be the timeline of rigor mortis, and how long would the blood remain liquid? Are there any other clues that would lead her to suspect that the woman was killed very recently, and not several hours earlier, as was reported?

Tracy Barrett, YA author

A: Once blood leaves the body it begins to clot very quickly. This process is completed in 5 to 10 minutes. After that, the blood begins to separate as the clot retracts into a dark knot and squeezes out a halo of yellow serum. This process would take another hour or more. The blood will then dry to a rusty brown stain. This could take several hours or even days in a moist climate.


As blood clots, the clot contracts, leaving behind the yellowish serum


You’re young slave girl could know this from her experience as a butcher. If she found blood that was liquid and still dripping she would know that the murder took place less than 10 or so minutes earlier. If she found that the blood had clotted but not separated then she might conclude that the murder took place more than ten minutes but less than an hour earlier. If the blood had separated into a clot and a surrounding halo of yellow serum, she would guess that the death occurred somewhere between one and three hours or so. Finally, if the blood had completely dried she might conclude that the death occurred at least 4 to 6 hours earlier, or longer in a moist environment. These are very general but should give you a usable timeline.

Rigor mortis would not play a role here since your corpse is found fairly quickly after death and it takes about 12 hours for rigor to fully develop. In this situation, the blood would more clearly define the time of death.



How Could My Time-traveling Physician Save the Life of My 15th Century Heroine With a Blood Transfusion?

Q: I am writing a time travel where one of the characters is a modern doctor who is sent back in time (15th century) with his family. I want to have him do something medical to save the life of the heroine (I was thinking heroine needs blood transfusion which would require a blood typing system) Any idea how it could be accomplished? I was also thinking that the heroine has rare blood type. Would that be Type B?

Doreen Jensen, Ontario, Canada

A: This is an interesting scenario in that you have someone with modern knowledge transported back to medieval times. This means he would have all the medical knowledge of transfusions––which of course did not exist then––but no scientific equipment to help. Not to mention that merely bringing it up might get him killed by the church––but that’s another issue.

The first human transfusion took place in France in 1667 when Jean-Baptiste Denis successfully transfused sheep blood into a fifteen year old boy. The first human to human transfusion was in 1818 and was performed by James Blundell on a patient suffering from postpartum bleeding. Even he had no way of matching the blood and, in fact, didn’t understand that there were blood proteins that made transfusions incompatible between many people and successful between others. It wasn’t until 1901 that Karl Landsteiner discovered the ABO blood groups and begin to understand the nature of transfusions and transfusion reactions. In 1939, the Rh factor was discovered, also by Landsteiner along with several other physicians, thus refining the process further.

So your time-traveling doctor would know all of this and would also know that transfusions are only successful if the donor and recipient match one another as far as blood type is concerned. But he would have no way of testing the donor and recipient for blood type and compatibility, which of course is essential to avoid harming or killing the recipient. But, there is a way around this. He would know that two compatible bloods could be mixed and no reaction would occur while if they were not compatible clumps would form. We call this agglutination and it is the basis of a transfusion reaction. He could simply mix the blood of the donor with that of the recipient––which is more or less the way it’s done today––and look for this reaction. The problem? This agglutination can only be seen microscopically and there were no microscopes in the 15th century.

The microscope was discovered in 1590 by two Dutch spectacle makers–Zacharias Janssen and his son Hans. They employed the glass lenses they used in their spectacle making, which had been around since the 13th century. When they placed these lenses in tubes, they discovered that they magnified any image viewed through the tube. This was the precursor of the true microscope which was developed nearly 70 years later (1660s) by Anton van Leeuwenhoek. So, your modern physician would know this and could perhaps fashion his own crude microscope from spectacle lenses. This would allow him to see any agglutination that might occur. He could then simply take the recipient’s blood and test it against several potential donors and see which one had the least reaction. This would be crude cross matching but it could work. He would then know whose blood to use in the transfusion process.


Q and A: How Would My 1925 Detective Determine That a Stain Was Human Blood?

Q: The setting is rural 1925. There are dark stains on trees, shrubs and leaves which my hero believes is blood. My questions are, how would he identify it as blood and how would he discriminate it from animal blood? What tests or experiments that existed in that era could he perform?

Frank James, Ste-Marthe-sur-le-Lac, Canada

A: The two steps needed to distinguish animal blood from human blood are: Determining if the stain or sample is indeed blood and then is it human of animal.

Testing liquids and stains to determine if they are blood is not new. For centuries, the microscope has been used to visually identify blood cells, which would prove that the substance is blood. But this required liquid blood and not the typical crime scene clotted or dried blood, neither of which contain identifiable cells. Several other tests appeared in the 1800s, including the hematin test, developed by Polish scientist Ludwig Teichmann in 1853. This also required liquid blood since in this test the blood was mixed with acetic acid and salt crystals, heated, and then viewed under a microscope. The presence of the characteristic rhomboid crystals proved the sample was blood. This test is similar to the present day Teichmann and Takayama Tests.

The guaiacum test, developed in 1862 by Dutch scientist Izaak Van Deen, used the guaiac resin of a West Indian shrub and is the precursor of the present day phenolphthalein test (see below). In the guaiacum test, the blood sample was mixed with hydrogen peroxide and guaiacum and, if it was indeed blood, a blue color would appear. In 1887, a similar test was used by Sherlock Holmes to identify a bloodstain in the very first Holmes story, A Study in Scarlet.


In 1900, Paul Uhlenhuth developed a serum that reacted only to human blood, and not animal blood. This is an antigen-antibody reaction and is similar to how this testing is done today. The sample would be dissolved in salt water and then the serum would be added. Human blood proteins would then react with the serum, producing complexes that would precipitate (fallout of solution) and darken the serum. Animal blood would cause no such reaction so if a reaction occurred the tester would know that the blood was indeed human and if not it must be animal blood or some other substance. Now we have serums that react with a just about any species of animal you can name and with these lab techs can determine the specific type of animal that shed the blood.

So your character could use guaiacum to determine that the sample was blood and then employ Uhlenhuth’s serum to determine if it was human or not.


Q and A: What Common Substance Could My Amateur Sleuth Use to Determine If a Stain is Blood?

Q: In my next mystery an amateur sleuth finds a stain on a wood floor under a rug. Is there a common substance she could use to determine if it were blood?

SCurran, Monroe, WI

A: There are a couple of easily obtainable chemicals that could be used for this. The first is phenolphthalein which was one of the first chemicals used to test for the presence of blood. It is readily available in most pharmacies and can be ordered online. There is a link below so you can see a company that sells the stuff and what it looks like.


Another thing that is purchased in any pharmacy are urine testing strips. These test for many chemicals but one of the things they test for the blood. There are several absorbent squares on the test strip one of which is a test for blood. Simply moistened the strip or moistened the staying and press the strip against the reaction will occur very quickly and this is a sensitive test for even small amounts of blood. Definitive testing to determine if it is indeed blood or if it is human blood or love a more sophisticated but these two testing methods are highly sensitive for even very small amounts of blood.

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Posted by on December 5, 2010 in Blood Analysis


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