What term refers to anything containing a mark to convey a message?

The term that best fits the description of anything containing a mark to convey a message is "document." A document refers specifically to a written, printed, or electronic record that provides information or evidence about a particular subject. This can include letters, reports, contracts, and other forms of written communication that are used to convey messages or preserve information.

In the context of crime scene investigations, documents play a vital role as they may contain important details about the case, such as witness statements, officer reports, and other relevant materials. They serve as official records that can be referred back to over time, making them essential for both investigative work and legal proceedings.

The other options, while related to the concept of conveying messages, do not encompass the same breadth or specificity as "document." For instance, "evidence" typically refers to information or materials presented to support a case but does not inherently imply a message conveyed through markings. "Communication" refers more broadly to the process or act of conveying information, rather than the physical manifestation of that conveyance, which is specifically captured in a document. "Record" often implies a more general collection of information and may lack the connotation of intentional messaging that a document carries.