Studies of anonymous-writing such as threatening letters, graffiti, or notes of any kind to determine authorship and authenticity is a function of handwriting examination and is done by a document examiner. A handwriting-analyst at Bureau Forensic Document Examination can provide comparisons of the anonymous writing to a group of possible authors to determine who penned the note.
Conducting a comparative study with possible authors can provide insight into an identification of the author, assuming the author is contained in the supplied sample set of potential writers. It is important to allow the document examiner access to all possible writers based on the circumstances of the situation. Allowing the handwriting-analyst to conduct a comparative study can lead writer-identification.