Footprints as Evidence in Criminal Investigation
Footprints are the chance prints left by the perpetrator at the crime scene. They are the impressions of the friction ridges found on the sole of the foot of human beings, that get imprinted on the surface on which the person has walked. The impressions formed are the result of Locard’s principle of exchange.
Footprints are unique to every individual just like the fingerprints. There is a possibility in the case of fingerprints that the culprit may erase the fingerprints or had worn the gloves so the fingerprints must not be available at the crime scene, but it is difficult to avoid footprints. To avoid the footprints the culprit may wear footwear but then the footwear marks are obtained which are also of evidentiary value at the crime scene.
However, footwear marks evaluation is one of the methods involved in forensic examination, which involves techniques differing from the footprint examination techniques.
Formation of Footprints
Since footprints are similar to fingerprints, therefore their anatomy, formation and types of occurrence at the crime scene are also similar. It is believed that the they are also formed due to the friction ridges present on the sole of the foot.
Also, The footprint science is based on the principle that no two persons have similar footprints. In other words, footprints are unique to individuals like fingerprints and can be considered as an example of Law of Individuality.
Skin of the plantar portion of the feet and toes are different from the skin of the other body parts. The papillary ridges present on the plantar surface form a unique pattern that constitute a footprint which contain individual characteristics. The friction ridges are formed at the fetal stage of every human individual and last till their lifetime. Therefore they are one of the reliable physical evidences in forensic examination.
The footprints found at the crime scene may contain unique features along with the ridge patterns. They can be phalange prints (formed by the phalanges and toes present at specific positions), crease marks (formed by the folds of the skin of the foot, which can be permanent or temporary), pits/corns/crack marks/deformity (these are not present in every individual), etc.
There is a unique condition related to feet in a few individuals (1.54% of the population) which is known as ‘flat foot’ where, complete instep region of the plantar surface of the foot is impressed on the surface. The curved area is not visible in such prints as in normal prints, which can be used as an identifying feature of an individual.
Examination of Footprints
The examination of footprints is conducted by the process of ACE-VR which is an acronym for- Analysis, Comparison, Evaluation, Verification and Report.
Analysis of footprints involves thorough examination of the footprints which includes the study of the margins, lines, shapes and position of various parts of the foot. There are few methods which have been developed for the examination of footprints. They are:
- Gunn Method- In this method, lines are drawn from the rearmost point of the heel to the foremost points of each toes present in the print. Also, a line is drawn across the most medial and lateral aspects of the ball of the footprint and observed.
- Optical Centre Method- Optical centres are marked on suitable points on the footprints and concentric circles are drawn around them. Lines are drawn between the optical centres of heels and toes.
- Overlay Method- In this method the outline of the footprint is marked and positioned on an unknown footprint and is compared by matching the characteristics like crease marks, shapes of the toes and their positions, scats, etc.
The footprints are compared using the overlay method of analysis which will help in establishing a match between the unknown and known prints. The process will commence in the order of-
Morphological analysis → placement of features → capturing the fine individual feature.
The compared characteristics are then evaluated according to the standards which decides whether the known and unknown prints are produced by the same individual or different individuals.
The next step after evaluation is the verification which is conducted by the different footprint examiners and then finally a report is submitted.
Footprints can elucidate the information about the link between the crime-victim-suspect, age of an individual, number of people present on the crime scene during the occurrence, movement of the victim or suspect on the crime scene, etc.
Admissibility of Footprints in Court
In India, Section 51 of Code of Criminal Procedure (CrPC) states that police can take the footwear of the suspect into custody to compare with the impressions found on the crime scene.
Section 5 of Identification of Prisoners Act states that the magistrate has been given the power to direct any person to submit his footprints for the fulfillment of procedure in CrPC for further investigation. If any person refuses such orders then he will commit the offence under the section 186 of Indian Penal Code.
There is no provision of footprints in the Indian Evidence Act (IEA) and no power is granted to court for trials. Section 73 of IEA only mentions the fingerprints and not footprints. However, section 45 of IEA includes the opinion of the expert of footprints along with other impressions.
Though the footprints have potential evidential value, still they are not admissible as reliable evidence in court. They are considered as corroborative evidence.
There have been many cases in India where the court stated that the conviction of the accused can not be based solely on the footprint evidence and the science of footprint analysis is not well established. The integrity of the footprint evidence, the collection procedure and the analysis is always questioned, therefore it is not considered as helpful evidence.