How Many Signature Samples Do You Need?

Forensic Document Examiner Studying With Magnifying Glass

When my clients first contact me, I am often asked how many signature samples for comparison will I need. The short answer is, the more the better. This may seem obvious to some, but I am sure that most clients want to know how much effort will be required on their end. Here are two significant reasons I cannot answer with a simple number.

ONE – Range of Variation

I want to understand how much variety the writer has. Without an adequate number of samples, I won’t know the writer’s range of variation. The best way to illustrate this is to take a look at your own signature under different writing conditions. No one writes the same way twice; you will recognize that in your own samples. How different are your signatures from each other? These differences are part of your range of variation. The more samples you collect, chances are that you will observe additional differences.

The range of variation is a significant factor in two ways. Fundamental differences of a disputed signature can be more obvious if the writer has a very consistent signature pattern that deviates only slightly from one signature to the next. On the flip side, a writer whose signature seems to vary wildly, also provides a basis for identification within the given range. Either way, the writer’s habits are present.

Knowing how consistently the signer writes helps us determine what to look for in the questioned signature.

TWO – Individuality

It is much more difficult to identify a writer if the genuine signature conforms to the styles learned in school or another popular writing style such as the rounded, loopy style of many teenagers. Most writers deviate from that style early on and establish their own patterns based on their ability and personal preferences. Some continue to write in what we call a “generic” style, requiring a more careful examination for slight deviations. Either way, a writer is identified by considering all the characteristics present and combining them.

So, when asked how many samples we need, the long answer is, as many as it takes to include all the characteristics necessary.  I may require far more samples of a generic writer than I do of a writer who has established a personal style.

The Answer – Let’s start with ten

As you may have figured out, this is an arbitrary number. If you are looking for signature samples and find more, great! If you come up short, we can start with what you have and see what more we need to support our opinion. The best ones will be those written around the date of the document in question. Really old ones are okay for reference, but handwriting changes over time, so look for the most contemporary samples.

I am happy to answer any of your questions. Email me at or just give me a call at 888-760-0339.