Areas covered: the forensic examination of signatures
The authentication of signatures is one of the most testing areas of forensic science. Signatures are very specialised pieces of handwriting and are frequently the targets of forgery. Unlike ordinary text handwriting, signatures contain only a small amount of comparable material. There are three critical requirements:
1. Proper laboratory facilities are essential*

*For further information see Information Sheet No 1 "The Scientific Examination of Questioned Documents"

I need specialised equipment to examine documents so I only do it in this Laboratory where proper facilities are available.

I will not travel to other laboratories to carry out examinations. I have equipment and instrumentation here of the highest standards, including image capture facilities that are not available elsewhere. I maintain it and have no need to share it, so my examinations can proceed effectively, quickly and efficiently.

So please send the material for examination here to this Laboratory. Do not be concerned about this. While they are with me, I shall store them in a secure safe and, unless we agree otherwise, shall only use non-destructive techniques to examine them. Your documents will not be damaged in any way.
2. The original document bearing the questioned signature

Ideally, I must examine the original signature, not a copy. A photocopy, facsimile copy, carbon copy or even a photograph is a poor substitute for the original - a copy does not show all the details of the original and, indeed, some copying methods are sometimes used as aids to disguise forgery. If I cannot examine the original questioned signature I may reach only restricted or qualified conclusions.
3. Genuine signatures for comparison

Signatures can only be compared with other signatures in the same name. Because an individual's signature varies from day to day, I need to examine a number of genuine signatures (ideally between twelve and twenty) to establish the natural range of that variation. These should be signatures made in the course of normal day-to-day business. Good sources of signatures are shown in the following table.
Document Type
Personal & Domestic

School/University/College Papers, Military Papers, Marriage Certificate, Divorce Papers, Old style Driving Licences and Passports (i.e. only those containing original ink signatures - see Note at the foot of this page), Personal Correspondence, Television, Cable and Satellite Rental/ Contract documentation, Car Log Books, Purchase Receipts, Receipted Invoices, Club Membership Cards (e.g. AA/RAC, Shopping Loyalty Cards, Library Cards), Insurance documentation relating to Household/ Household Contents/Office/Car/Health Cover, Inland Revenue Tax Forms.
Shopping & Commerce

Credit Card Sales Slips, Credit Cards, Credit Card Application Forms, Loan Application Forms, Hire Purchase or Rental documentation
Financial & Banking

Cancelled Cheques, Bank Specimen Signature Cards, Mandates, Guarantees, Standing Order Forms, Direct Debit Forms, Building Society Withdrawal/Paying-in Slips, Transfers, Post Office Savings Books, correspondence with Bank and Accountants

Job Application Forms, Employment Contracts, Personal Appraisal Forms, routine work Letters and Memos, Files, Sick Notes, Holiday Request Forms, Time Sheets, Petty Cash Claim Forms, Security and Identity Cards, Accounts Ledgers, Sales Ledgers, Bought Ledgers, QC Records, Invoices, Order Forms
Social Service & Health

Unemployment Benefit Forms, Supplementary Benefit Claim Forms, Pension Allowance Forms, Consent Forms, Operation/Treatment Forms, Discharge Forms, Doctor 's Prescription Forms, Dental Record Forms for Treatment or "Signing On"

Wills, Conveyances, Mortgage Application Forms, Mortgage Deeds, Affidavits/Statements, Agreements, Assignments, Powers of Attorney, Contracts, Leases, Promissory Notes, Partnership Agreements, Witness Statements, Statements to Police, Legal Aid Forms, documentation submitted to a Court, correspondence with Solicitors

Statutory Companies House Forms, general company documents such as Accounts, Balance Sheets, Stock Transfer Forms, Share Certificates, Minutes of Meetings
Signatures made close in time to the questioned signature are particularly helpful (and this is very important if the person involved has been ill or is elderly). Photocopies of signatures alone are not adequate - I must be able to examine some original genuine signatures to establish the detailed structure of the signature. However, do not discard documents which are only available as photocopies - these can be helpful. When in doubt send everything; I shall be able to select the relevant material.
4. Documents which are generally NOT helpful in the forensic examination of signatures

Modern Passports and Driving Licences
The signatures on these documents are generally NOT helpful. These signatures are merely low quality, reduced copies of signatures made on an application form. The application form itself often compounds the problem since the writer is compelled to confine their signature in a restricted box, thereby potentially making the signature unusual. However, again, I am prepared to review such signatures in case they can be used.

The Giles Document Laboratory