Institute of Criminology and Expertise PZ: Each signature is an individual manifestation of the signing behavior of the given person

The first part of the interview about the Digital Signature Pad (DVP), police work, and international cooperation with handwriting experts from around the world can be found HERE.

What is the difference between KEÚ PZ and private handwriting experts? When does a case come to you?

Private handwriting experts are listed in the registry of experts, interpreters, and translators maintained by the Ministry of Justice of the Slovak Republic, in the field of Handwriting Expertise or the field of Criminalistics, under the branch of Handwriting and Signature Forensics. KEÚ PZ is also registered in this field as an expert institute, and the experts in our department conduct their forensic activities as experts in the branch of Handwriting and Signature Forensics. It is up to the party requesting the examination whether they invite a private handwriting expert from the list or KEÚ PZ or another expert institute.

Regardless of DVP examination, our institute has state-of-the-art laboratories, our examinations are accredited by the accreditation body, we conduct annual competency testing exercises both internally and internationally, and we are members of the aforementioned ENFSI network. The cases we handle are highly diverse, as we primarily work for law enforcement authorities (OČTK) and courts, giving us extensive experience with various approaches to examinations.

For law enforcement and criminal courts, we prepare reports free of charge. This, or some aspects of it, may distinguish us from individual private experts or other expert institutes. Only an expert institute can prepare a control report on the forensic findings of other experts.

What is the difference between DVP and a traditional paper signature from a handwriting expert’s perspective?

Both types of signatures are defined as the most automated, handwritten expression of the signer. Every signature is a specific manifestation of the signing behavior of the individual, which the person develops over the course of their signing practice. This behavior is, in principle, individual to each signer and is influenced by psychosomatic specifics, health conditions, frequency of signing, and more. The signing behavior and the signatures within it are unique due to these factors, which is the foundation of handwriting expertise aimed at identifying the signer. Both types of signatures generally serve the same function, authorizing some information content through the act of signing.

However, for handwriting experts, these are different types of traces, which lead to distinct security, methodological, technical, and other specificities in the examination. A traditional signature on paper requires an original on a paper document or list so we can examine all the characteristics of that signature. In contrast, for DVP, we need to obtain numerical (biometric) data that make up the signature, including at least the basic data for static shape, pressure, and time of execution, ideally exported into a CSV file. It is not sufficient to provide us with PDF files, whether printed or in electronic form.

Is DVP easier to examine than a traditional paper signature? How do you examine DVP? Are specialized tools available?

It depends on what we consider in terms of the complexity of the examination. As mentioned above, in terms of procedures, technical requirements, and expert qualifications, examining DVP is more complicated. Forensic (analytical) software is also involved in the examination process, allowing DVP to be visualized or various DVP properties to be represented in other ways. It is used to analyze and compare DVP in a manner similar to traditional signatures, but in a different environment. However, if the expert receives the necessary data for examination, the DVP analysis can lead to more robust, quantifiable, and easier-to-demonstrate findings, thereby more strongly supporting hypotheses regarding the authenticity of the DVP or its signer.

How long, on average, does it take to examine a DVP signature? And how long for a paper signature?

It depends on the complexity of the case and the number of traces that need to be examined, documented, processed, evaluated, etc. A simple case can take a few days, an average case several weeks, and there are complicated cases with numerous traces that we examine for months.

The length of time to examine a DVP case, once we have everything we need, should not differ significantly from the time it takes to examine a case not involving DVP.

How do you handle situations when you only have one or no comparative DVP from the person whose DVP you need to verify? Can you compare DVP and paper signatures, or obtain additional comparative DVPs?

In the case of disputed or contested DVPs, the ideal comparative material is genuinely authentic DVPs from the person obtained from objective sources, DVP tests made for the purpose of the examination, and traditional signatures of the person on paper. Since it is still common not to have additional DVPs from the signer’s usual practice, the solution is to conduct DVP tests using the same or an equivalent combination of digitizer and software that was used to create the disputed DVP.

The comparative material is further supplemented by traditional paper signatures that meet certain conditions, which is more or less standard procedure. In any case, it is best for those requesting the examination to consult the case with us in advance and determine what materials need to be secured, as cases are individual. Sometimes, securing the traces in a certain way is not necessary, while in other cases, it is.

What is the outcome of your examination—can you determine a 100% match between the disputed DVP and the comparative signatures, i.e., verify the authenticity of the disputed DVP 100%?

This is a common misconception among laypeople about DVP and signature examinations in general. This is contributed to by the marketing of software tools that automatically evaluate the match between a DVP and a database of reference DVPs, which some companies use to authenticate clients or verify their identity. These software tools work on algorithms that evaluate the similarity of a DVP based on certain features with an input reference group of signatures.

Depending on their sophistication, these tools can contribute to verifying the authenticity of a given DVP or serve as one of the tools for identifying the signer, along with other authentication tools. However, these algorithms only work to a limited extent with the properties of specific signatures; they cannot evaluate the signer’s overall signing method, natural variability, or the impact of external or internal conditions during signing, and so on. Thus, they can only be considered a filter, if anything. The signing method falls under behavioral biometrics—each signature within the signing method is different, but it carries certain consistent traits precisely because it is an automated behavior. Only a handwriting expert can evaluate these consistent traits comprehensively.

At the moment of creating a DVP, various influences affect the signer, whether physical conditions or mental state, health conditions, potential deliberate intent, etc. All of these factors, and more, cannot be evaluated and assessed by automation.

At the KEÚ PZ Department of Handwriting and Language Expertise, we do not quantify the conclusions of our examinations; instead, we express them verbally. The examination conclusion consists of findings that we objectify in our expert report by clearly demonstrating and describing them. This is the objective part of the examination. The subjective part is added to this, where the handwriting expert plays an important role with their education, qualifications, and experience. The handwriting expert assigns a certain identification value to their findings within the framework of the established hypotheses and formulates the examination conclusion. Although the conclusion is clearly stated, it is not a determination of factual fulfillment, as this can only be done by the decision-making authority. It is a qualified opinion from an expert, who, based on demonstration and reasoned interpretation of their findings, provides evidence of a certain fact.

We will bring the final part of the interview in a future blog. You will learn what recommendations the experts give to companies and signers and how they assess the current practice of signing documents remotely.