Stringing Bloodstains: The Old School Method

string sideWe’ve got the fabulous Tom Adair back to answer any and all questions about the fascinating intricacies to blood spatter analysis! 

From investigating the shootings at Columbine High School to locating grave sites in the remote back country of the Rockies, Tom Adair has lived a life most crime authors only write about. While in law enforcement he was board certified as a senior crime scene analyst, was one of only 40 board-certified bloodstain pattern analysts and one of 80 board-certified footwear examiners worldwide. Over his 15 year career he has been interviewed by and consulted for television, text books, novels, magazines, and newspaper articles as well as documentaries on the Discovery Channel and National Geographic.  He’s also the author of recent crime thrillers The Scent of Fear (2012) and Bloodlines (2013). He runs the BLOG forensics4fiction as a resource for authors to understand forensic science and law enforcement issues. 

Bloodstain Pattern Analysis (BPA) is a critical component of Crime Scene Reconstruction (CSR). Many authors associate blood evidence with DNA but, DNA only answers the “who” question. The bloodstain patterns themselves may answer the “what”, “where”, “when”, and “how” questions. An analysis of bloodstains can reveal any number of issues such as the movements of bleeding subjects, sequencing of events, minimum number of bleeding subjects, minimum number of blows from a weapon, and much, much, more. It’s not uncommon for analysts to spend hours, even days, at a crime scene just examining the bloodstain patterns. I once spent nearly a week at the scene of a double homicide just documenting bloodstains! It can be very labor intensive but the work is rewarding if it clarifies critical questions.

One determination analysts may be tasked with is the determination of an “area of origin”. This is an approximate location in 3-dimensional space where a particular spatter pattern originated. This may be the relative position of a victim when they receive an injury that produces blood spatter on an adjacent surface like a wall. Determining this area of origin can shed light on a number of factors including the height of the event. You see, by measuring the shape and orientation of a blood drop we can determine the angle of impact (ex. traveling upward to the right at a 20 degree angle). When we compare the impact angles and directionality of several drops in a pattern we can back track the trajectories to a common convergence in space. This can provide critical information to investigators. For example, if the area is located a foot off the floor it’s proof that the victim was not standing or kneeling at the time the injury was inflicted.

But data on a page or spreadsheet doesn’t help others in understanding the nature of these convergences so analysts have developed ways to “demonstrate” this convergence visually. Modern techniques utilize computer programs and CAD programs to replicate these findings. The visuals can be helpful in court but they may come off as a bit “sterile” in my opinion. I’ve always preferred an older method called “stringing”. Essentially, after determining the angle of impact and directionality of the stain, the analyst attaches a colored “string” to the point of impact and runs it backwards to a termination point (like the floor). After attaching a number of these strings the area where all the strings cross can be photographed and used in other reconstruction events on scene. I should note that this process isn’t begun until all of the samples have been properly documented and collected. It is generally one of the last tasks done by the analyst.

The advantage to this technique is that the analyst can visualize this “event” in the real context of the crime scene and measure that event against other evidence found on scene. That process is more difficult on a computer screen back at the crime lab.  Investigators can consider various scenarios and role play possible actions to create the blood patterns found in context of the actual crime scene. Now there are some limitations to this technique. It’s not useful for certain types of bloodstain events like passive staining, cast-off, or contact transfer stains. Also, blood droplets in flight eventually succumb to gravity and their flight path changes. Once that occurs back tracking that flight path becomes very difficult. Too many unknowns such as mass/velocity.  Another “danger” is the possibility of some clumsy person damaging the strings during the process. What happens when a clumsy patrolman comes into the room and trips over your strings? Hours of work lost!

So if the injury occurs close (within a few feet) to the surface (wall, ceiling, furniture) then the technique can be very useful. The main thing to remember is that the results of such an exam are visually stunning and demonstrated in real space (the crime scene). The investigators can “see” the convergence from all angles and perspectives which is a wonderful tool in reconstruction. In the future we may see the ability for investigators to use holographic projections to simulate the findings thereby removing the possibility of inadvertently damaging the strings.

Here’s a blurb from Tom’s most recent release, Bloodlines:


Bloodlines CoverCSI Sarah Richards is back in the heart pumping follow up to The Scent of Fear. Months after the assassination of Governor Hoines, a determined genealogist stumbles upon a conspiracy that threatens to expose a plot to reshape the nation by a rich and cunning family in Colorado. Now the Gerovit, an elite group of Russian assassins returns to destroy any evidence of the conspiracy. As Sarah’s mentor and his nephew Daniel crisscross the nation trying to unravel the genealogist’s coded journal, Sarah must discover how two double murders separated by a century are connected to the most powerful man in Colorado. But with enormous political forces, a team of killers, and her own department working against her, can Sarah unravel the clues before she becomes a part of history herself?

Some gals are musician groupies.  Others are fascinated by all things Hollywood.  For me, it’s forensics 🙂  Plotting that perfect crime?  Wondering where TV gets it wrong?  Fire away and Tom will try to answer your questions!

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6 Responses to Stringing Bloodstains: The Old School Method

  1. Willa says:

    Welcome 😀

    I would like to ask – have you ever watched any of the CSI programmes and what do you think about them? Because the world and his wife now think they are CSI’s! Do you think they have given advantages/knowledge to criminals?

    And my second question – yes, I am greedy – is, I notice your book/s are written from the POV of the female protagonist – how hard do you find this and what made you take that decision?

    Many thanks – and thanks for the great work you did.

    • Tom Adair says:

      I used to watch the old CSI:Las Vegas episodes but haven’t in years. These types of shows have changed how CSIs are perceived in public and now it is common for us to have to testify as to what is commonly referred to as the “CSI Effect”. Basically we have to dispel certain inaccuracies in these shows to juries so they don’t have false perceptions of the reality of our work. I’ve never been worried about these types of shows “educating” criminals to the point it affects our abilities to do our jobs. Most criminals aren’t savvy and many crimes are committed without major pre-planning. There is a ton of information out there for criminals to access (peer reviewed journals for example) and I haven’t seen any detrimental effects.

      As to your second question, it is both difficult and rewarding to write a female POV. When I began formulating these stories it became apparent that they could only be told from that viewpoint. Women are the fastest growing demographic in forensics and many crime labs are now majority female. Women face certain challenges that men simply don’t have to deal with (some exceptions of course). At the same time, being a male, I am challenged to make her “convincing” and I spend an inordinate amount of time focused on the things that are important to women “like” Sarah and talking to women that reflect her character. In my final WIP (the final of the Gerovit trilogy) Sarah and Daniel are facing monumental personal and professional challenges that require me to do a lot of research and interviews I didn’t expect. All things considered though, I wouldn’t have it any other way.

      • Willa says:

        Thank you for the great reply. Just been to your website and noticed there are no excerpts . . are they written in first person? I also like to check the excerpts to get a feel for an author’s voice 😉

  2. kendraelliot1 says:

    Hi Tom, can you recommend some texts for authors to use as resources when researching blood spatter or other forensic aspects of crime scene investigation?

  3. Tom Adair says:

    I highly recommend Bevel and Gardner’s text on BSPA and CSR. Here’s the link.

  4. Hi Tom … I’m teaching forensic science for the first time and have done some research. I agree with your assessment of the CSI programs, but how would you counter the tendency these shows engender for instant gratification? How would you “grab” students’ interest on the first day?

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