The NYT of June 30, 2015 includes an article on the investigative value of the check register. Generally, the register comprises a ledger / writings on the cash inflows and outflows of the person, including brief explanations as to the purposes of these flows of funds. However, they are rarely sufficient for the purpose of criminal prosecution / defense without robust and corroborative extrinsic records (e.g., bank statements, loan documents).

This issue of whether information held by banks contains adequate information with which to assess probable cause of the existence of a specific crime and specific criminal occasionally is resolved against the bank where suspicious activity is ignored. See Madoff’s relationship with JPMorgan. If no cash transactions were to fall outside the bank’s domain of information (e.g., disbursements from a petty cash – currency fund), then banks would be in the position to assist greatly in the investigation of financial and other crimes. Cf. imprest fund.

Cash in the form of currency and coin allows the criminal / tortfeasor to work outside the supervision of intermediaries and custodians such as depository banks and other financial institutions. Activities ranging from accumulation of proceeds from transactions in controlled substances and contraband (i.e., cash on delivery) to financing of acts of terrorism without adequate audit trail (e.g., paying aiders and abettors in currency) may be one or more steps removed from bank records. Privacy and confidentiality are protected against detailed monitoring by financial institutions and law enforcement. Cf. Hastert.

If every dollar / unit of foreign exchange were traceable to a bank statement of account, law enforcement agencies’ ability to develop cases would be enhanced by the surreptitious nature of working through the bank. Cf. obtaining communications data from intermediaries such as phone companies and Internet service providers.