Patterns in blood, such as ridge detail or footwear impressions, can be enhanced through the use of Amido Black.  Amido Black is a general protein stain.  It will react with proteins found in blood, but is not specific for blood.  The use of Amido Black results in a dark blue to black staining of the protein that can enhance the contrast and visibility of patterns and impressions and allow for easier documentation.

In the images below, treatment of a painted cement floor with Amido Black revealed an apparent tread pattern in blood.  The tread pattern on the boot appears similar enough to the tread pattern observed on the floor that the crime scene team would collect both for possible testing by the Trace Section.