Question Document Investigation (QDI) is a vital part of forensic science and criminal justice and is used to analyze handwritten and printed documents in order to uncover facts and opinions. QDI is used to detect fraud, determine authorship and to certify authenticity of documents.

The investigation uses methods such as examination of handwriting and ink, examination of chemicals, physical examinations, and comparing texts or handwriting to reference samples. Questioned document investigations are often used to determine the age and origin of documents, authenticate signatures, and analyze document content.

QDI can be broken down into three distinct phases: preliminary examination, working examination, and final examination. During the preliminary examination, the examiner will look at the entirety of the document and analyze it to identify any areas of interest. Once these possible areas of interest are identified, the examiner will then move on to the working examination. During this section of the investigation, the document analyst will use tools and techniques to analyze the questioned documents in order to uncover any additional information such as authorship, date and time of creation, and any alterations. Finally, if necessary, the examiner will move on to the final examination, where the document will be examined in more detail and additional evidence will be thoroughly analyzed and documented.

Questions Documents Investigation requires the knowledge of several scientific methods and tools in order to effectively analyze documents. High-powered microscopes, magnifying glasses, and specialized chemicals are among the most common tools used by document examiners in order to detect problems with documents. In addition to understanding how to use these tools and equipment, document examiners must also understand how to interpret the results of their findings, including interpreting the structure and characteristics of handwriting and determining if documents have been altered as well as determining whether certain prints or signatures are authentic or forged.

Due to the sensitive and precise nature of QDI, the standards used are some of the highest in the forensic science field. Document examiners must adhere to the standards set by the American Society of Questioned Document Examiners (ASQDE), a professional organization that promotes the highest standard of practice for the field.

In the end, Question Document Investigations are a crucial component of forensic science and criminal justice. It is used to detect fraud, determine authorship and to certify authenticity of documents. It is important that all document examiners maintain the highest degree of accuracy and integrity in the practice of Questioned Document Investigation in order to ensure the most reliable evidence and results are obtained.