When crimes such as murders take place, more often than not there will be blood present at a scene. At the crime scene of a particularly brutal murder there will most definitely be pools, sprays and droplets of blood. By analysing these bloodstains, forensic scientists can reconstruct the events which took place.

The way blood falls can tell us a lot about a crime scene. By simply examining any droplets or smears we can establish exactly where the crime took place, how the crime took place, and even in which direction the victim and assailant were facing at the time of the murder. When blood falls straight down to the ground it takes on a spherical shape, though if the floor is of a rough surface it will take on more of a star shape. When a droplet of blood strikes the wall or floor at an angle, it will become elongated and oval. From examining these stains we can even determine at what angle the blood landed.

As most criminals are unaware, it is impossible to eradicate all traces of blood completely. Though they can clean up after the crime and be satisfied that they can see no blood, there are always ways to find it. Forensic scientists have several chemical methods at their disposal to detect blood. Some of the most common methods are the Phenolphthalein or Peroxidase test, the Kastle-Meyer test, and the Luminol test. Luminol is a chemiluminescent that, when used on suspected blood in dark conditions, will fluoresce if there is in fact traces of blood there. For the Phenolphthalein test Phenolphthalein, potassium hydroxide and distilled water are added, boiled, and then powdered zinc is added. A few drops of this solution on the suspected blood will turn pink if positive for blood. Another Phenolphthalein test is Phenolphthalein mixed with orthotolidine, which works the same way. Another chemical used in blood detection is Leucomalachite, which appears green if blood is present.

For Centuries bloodstain analysis has aided in the investigations of homicides and, as more time passes, new ways of detective and analysing blood are becoming available to forensic scientists.

Read up on some of the crimes that have been solved with the help of bloodstain analysis:

Lynne Chamberlain