Law and Public Safety

Law and Public Safety

Impressions Unit

Impression Evidence

One of the most influential philosophies behind modern forensic science, commonly known as Locard's Exchange Principle, states that, "with contact between two items, there will be an exchange." True with Fingerprints and DNA, this is also true with impression evidence, an important and sometimes overlooked aspect of the criminal investigation process.

Impression evidence may include shoe prints and tire tracks, both two- and three- dimensional. When properly collected, such evidence can later be compared with other like impressions or suspected origins in the St. Louis County Police Crime Laboratory. The range of conclusions for such examinations includes:

Identification (definite conclusion of identity)

The impression in question was either made by the suspect shoe/tire, or the impression in question was made by the same shoe/tire as the other impression.

Probably Did Make (very high degree of association)

The impression in question corresponds in design, physical size, and general condition of wear with the suspect shoe/tire or other impression, but existing individual characteristics are not sufficient to enable certainty of identification.

Could Have Made (significant association of multiple class characteristics)

The impression in question corresponds in design, physical size, and general wear with the suspect shoe/tire or other impression, but it lacks individual characteristics.

Probably Did Not Make (very high degree of non-association)

The impression in question has dissimilar features than the suspect shoe/tire or other impression, but limited detail in the impression in question precludes elimination.

Elimination (definite exclusion)

The impression in question was either not made by the suspect shoe/tire, or the impression in question was not made by the same shoe/tire as the other impression.

Unsuitable or Inconclusive

The impression in question lacks sufficient detail for comparison purposes.

After a case is worked, an Examiner will write a detailed report concerning scientific findings related to the impression evidence analysis. Then, upon request, the Examiner will testify in criminal proceedings based upon these findings as an expert witness in the area of Impressions examinations.


Shoe and Impression (photo courtesy of Zalman992/wikimedia)

For more information, please contact:

St. Louis County Police Crime LaboratoryASCLD Logo
Lieutenant Dana Fulton, Commander
Telephone: (314) 615-5365
E-mail: [dfulton@stlouisco.com]

Ms. Lisa Campbell, Deputy Director
Telephone: (314) 615-5365
E-mail: [lcampbell@stlouisco.com]

7900 Forsyth Blvd.
St. Louis, MO 63105
Fax: 314-615-8956

Hours of Operation:

Monday – Friday, 8:00AM to 4:30PM*
The Laboratory is closed on all St. Louis County Government holidays
*Please call for an appointment if submitting evidence


St. Louis County Police DepartmentCALEA Logo
7900 Forsyth Boulevard
St. Louis, MO 63105

Emergency Calls: Call 911
Non-Emergency Reporting / General Information: (314) 889-2341
TDD: (314) 889-2345