Blood Spatter Analysis

Purpose:

The purpose of the Blood Spatter Analysis Lab is to learn how to analyze and decipher unique details from different types of blood spatters. Preparing us for our crime scene final exam, by increasing the quality of a reconstruction of a crime. In end this lab improves our crime scene analysis skills and our ability to recreate a reasonable crime scene and make a conclusion also aiding us in identifying victims and perpetrators.

Materials:

- Construction Paper

- Bottles you can squeeze (for the blood)

- Fake blood

- Tape

- Pencil (NOT PEN)

- Calculator

- Notecards

- Metronome

- Protractor

- Small piece of wood (Like a small 2 inch wide or similar plank)

- Tape measure or meter sticks

- Long roll of paper

Procedures:

Single Blood Drop Pattern:

Place a measuring stick on the ground flat against a wall vertically
Use tape to secure the measuring stick
Place a note card under the measuring stick
Grab a squeeze bottle of fake blood
Hold the bottle nozzle down 20 cm over the notecard according to your measuring stick
Barley squeeze the bottle, just enough to get one drop out
Rapidly flip the bottle after the drop comes out as not to let anymore than one drop out.
Remove the current notecard and let it dry
Label the notcard with the height its blood was dropped from
Repeat steps 3-9 for the other measurements of 40cm, 55cm, 80cm, 100cm, and 150cm
After finishing every height use a ruler to measure the diameter of each blood sample (IGNORE THE PROTRUSIONS FROM THE MAIN IMPACT)

Multiple Blood Drop Pattern:

Place a measuring stick on the ground flat against a wall vertically
Use tape to secure the measuring stick
Place a note card under the measuring stick
Grab a squeeze bottle of fake blood
Hold the bottle nozzle down 40 cm over the notecard according to your measuring stick
Barley squeeze the bottle, just enough to get one drop out twice, making the puddle two drops big
Briefly flip the bottle look at puddle
Quickly Put the bottle at the 40cm mark again and repeat step 6 to make a 4 drop puddle
Use a ruler to measure the diameter of the blood sample (IGNORE THE PROTRUSIONS FROM THE MAIN IMPACT)

Walking Drip Pattern:

If you have access to a room that you are okay with it getting a little messy use that (Tile floor with easy clean up)
Use a long roll of paper and lay it on the ground
Measure around 14 feet of paper to use
Tape paper to the floor to keep it from moving
Hold the bottle by your side with the nozzle face down
If you are in a room that can get messy start walking a few feet behind the the paper pressing the bottle lightly
(IT IS IMPERATIVE TO THE ACCURACY OF THIS TEST TO WALK HOW YOU NORMALLY WALK)
Walk from a few feet before the paper to a few feet after leaving a trail of blood
If you do not have a room you can use for the mess, then start the walk on the paper and end on the paper, and be careful using the first part and the end part of the experiment as it is inaccurate because you were standing and not walking yet

Vertical and Horizontal Arterial Spurts:

For Vertical
Roll out 14 feet of paper
Find a flat wall that can fit this paper
Tape the paper to that wall
Turn on a metronome at 80 bpm (median of average adult heart rate)
Walk along the paper at a normal pace holding a blood bottle a few inches from the wall
Squeeze the blood bottle lightly every time you hear the metronome's beat
For Horizontal
Tape 14 feet of paper to the floor
Hold a blood bottle nozzle down at your side
Start walking before the paper
Once over the paper every metronome beat you hear squeeze the bottle lightly similarly to the vertical
(IT IS IMPERATIVE TO THE ACCURACY OF THESE TEST'S TO WALK HOW YOU NORMALLY WALK)

Impact Angle Bloodstains:

Tape a meter stick up the wall
Use a small piece of wood and attach a notecard to one side of it at the top
Adjust the wood piece to the wall right next to the meter stick and adjust it with a protractor to the correct angle.
Make sure the notecard is on top and at the end closest to the wall where the meter stick is.
Tape the board to the wall
Look at the top of the board and align it to a specific height of the meter stick. Add 30 cm to this height for all of the angles in this lab. This is where the tip of the squeeze bottle will be.
Put the bottle in that location, ensuring that when squeezed, the drops will fall on the notecard.
Drop one drip and put the bottle down. You will not need it until the next adjustment is made. Let it sit for 2 minutes, then carefully pick up the paper so that the length and width of the drops do not change.
Repeat the lab for angles 20, 30, 50, 60, 80, and 90. Then measure the width and length of the impact drops and determine the angle using arc measurements.

Data Collection:

Single Blood Drop Pattern:

On the left you can see all of my tests and on the right you can see my setup, which is a 2 meter sticks pushed against the wall and taped and then the blood lands perfectly on the paper when dropped.

Multiple Blood Drop Pattern:

The multiple drop test had a much bigger diameter and a irregular shape compared to the near perfect circles from the single drop experiment. The multiple drop experiment was set up in the same way as before using 2 meter sticks up against the wall using tape to keep them in place on each other and make it super easy and accurate to drop the blood from higher heights.

Walking Drip Pattern:

The walking drip pattern was easy to set up, roll out the paper put the bottle to your side and walk! However we did come up with some ideas to make the data more viable, when you just start the walk the blood gets a little messed up because you are going from walking to standing, but if you start before you are on the paper and end after the paper you would not have this problem. One thing I noticed during this experiment is the pattern that is displayed when walking, you can see gaps in the blood and sometimes double trails, that normally happened on the second step because the persons arm went backward over ground they already covered, both creating a gap and a double trail.

Vertical and Horizontal Arterial Spurts:

The vertical and horizontal arterial spurts were an easy set up and experiment. For the vertical I was the one walking with the blood and I found that our bottles are way more sensitive than I thought and I squeezed the bottle way too hard on the first squirt, the rest were softer and consistent. One notice about the vertical is that they all have a very visible drain line where the blood dripped, additionally they have splat marks surrounding the big blood spot.

Horizontal was easier as we just had to walk over the paper and we already knew not to squeeze too hard. I found with the horizontal it was really spaced out and basically looks like the reugular walking one but with harser drops and only every few steps.

Impact Angle Bloodstains:

The impact angle blood stains were easy to do and run the experiment, the hardest part was getting it to stick at the right angle, but once we did it one or two times it got easy. The results had a pretty common pattern, the higher the degree the longer the drip, for example 0 degrees didn't flow at all but 90 degrees needed specials paper to make sure it could flow all the way.

Data Analysis Calculations:

Using the data we got from the impact angle lab we could find out exactly what angle each impact blood mark had, this is a useful technique in a crime scene because you could use calculations to figure out what angle the blood came from to find out how a person was killed or how they fell which is useful for determining a suspect and solving a death in general. Our calculations were very close to what the actual degrees were for the lab proving that this is a good method of determination and will work in real life scenarios.

Conclusion:

In this lab I utilized my understanding of biology and chemistry to research and understand a lab thoroughly before starting because this lab happened very quickly and if you didn't know what your next step or what calculation you have to make you would be throw very far behind in the experiment. After this lab it is clear the implications is has in a real world scenario, it shows us just how scientist solve crimes whether it's how dry the blood is, or the size of the blood drop helping them find out how far up it was dropped, or maybe the length of a blood trail dripping down an angled surface helping them figure out what angle the blood came from, or it even could be a blood on the ground and they wanted to find out whether the person was arterial bleeding or bleeding somewhere else. Regardless of the use, there is so many things the techniques learned in this lab could be used for.

Reflection:

This lab was really fun! It was quick and painless, the only difficulty I ran into was squeezing the bottle too hard and getting it all over myself. I wish we could have had more time to learn of other methods because I know there are definitely other methods we didnt learn that could be super useful and fun! But I really did have fun with this lab and I can't wait for the final lab where I can put these techniques to use on a real crime scene.

Lab Sheet:

3.1.5. Blood Spatter Lab - CSIForensic Techniques.pdf

Page updated

Report abuse