Local police walked through our Library earlier today with no explanation. Later on, we noticed 2 teens on premises, who we assume should have been in school. We thought the police may have been looking for them as truants, but that is not confirmed. The question is, if the police were to ask if we saw the teens, are we able to answer or is that considered a violation of patron privacy as it is with patron information and records?
There is no one right answer to this question, but there is a formula for any library to come up with its own, unique answer.
Here is the formula:
[Situation] x [Ethics + Law] / [POLICY/Precedent] = YES or NO
Let me break this approach down. And trust me, I will give a clear reply to the member's question at the end of all this.
The formula starts with the situation. In the scenario we have here:
"Local police walked through our Library earlier today with no explanation. Later on, we noticed 2 teens on premises, who we assume should have been in school. We thought the police may have been looking for them as truants, but that is not confirmed."
There is a lot that can be said about this description, but one important aspect of it is the library's care to not reach a conclusion about why the teens were at the library instead of school (while the member describes an "assumption," there is no action on that assumption). And as noted, law enforcement was not called; rather they "walked through...with no explanation."
This situation is then multiplied by the combined factor of ethics and law. Both the ALA and NYLA Codes of ethics emphasize patron confidentiality. Meanwhile, New York's Civil Practice Law and Rules ("CPLR") Section 4509, the state law requiring a subpoena or judicial order before a user's library records can be shared without that patron's consent, does not define "library records" other than to state that they include "personally identifying details." This is why whatever the situation, ethics, and law are, the answer must be assessed under a library's policy governing patron records (while considering past applications of the policy, to ensure consistent application).
It is at this last factor--policy--where things can get complicated. With the advent of (sorta) new technologies, the definition of "library records" is not just internet searches and checked-out materials. It could be what a person printed on a 3D printer, or their image on a surveillance camera, or their use of library wi-fi. None of these things, right now, are listed in CPLR 4509, but many library professionals would consider them to be library records.
The trick is making sure that when a library takes a position about library records (especially with regard to records that, at first glance, are not about library services, but more about security), it is supported by their policy.
Okay, I know I promised a "clear answer". So let's re-state the question: "if the police were to ask if we saw the teens, are we able to answer or is that considered a violation of patron privacy as it is with patron information and records?"
Based on a fictitious library consulting a fictitious lawyer, here is one possible answer:
To the ABC Library:
You have requested legal advice regarding whether a library may provide a substantive answer in response to law enforcement enquiring about the presence of a patron in the library.
Your concern is that such a disclosure, based on the visual observations of library employees rather than written/recorded records, could still be considered a violation of patron privacy. You confirmed that at the time of the inquiry, the library had no operational need to release any such information.
I have reviewed the library's policy on patron confidentiality, and based on the below clause, I advise to not release such information unless there is a subpoena or judicial order:
"Consistent with the ALA and NYLA Codes of Ethics, the ABC library considers any record or information that indicates an individual's use of library services and/or facilities to be a library record under CPLR 4509, unless specifically excluded by this policy."
Therefore, I advise not providing such information without a subpoena or judicial order, unless the requestor accurately points out that a specific law requires it.
Thank you for trusting me with this question.
Very truly yours,
A. Hypothetical Lawyer, Esq.
Of course, as the "formula" at the start of this answer points out, the "situation" may vary from time to time. And CPLR 4509 does leave room for mandatory disclosure "when otherwise required by statute."  Those are the times when a library may want to consult a local attorney to obtain quick advice in the moment.
Since this formulaic balancing of facts, ethics, legal obligations, and policy can be difficult to keep in mind, it may be helpful to summarize it to library trustees, employees, and volunteers this way: “A patron's use of the library and our services are confidential. If anyone asks about a patron using or being at the library, our standard reply is 'Since patron information is confidential, I need to refer you to [the Director].’”
Thanks for a very thought-provoking question.
 As of November 12, 2021, here is the text of CPLR 4509: "Library records, which contain names or other personally identifying details regarding the users of public, free association, school, college and university libraries and library systems of this state, including but not limited to records related to the circulation of library materials, computer database searches, interlibrary loan transactions, reference queries, requests for photocopies of library materials, title reserve requests, or the use of audio-visual materials, films or records, shall be confidential and shall not be disclosed except that such records may be disclosed to the extent necessary for the proper operation of such library and shall be disclosed upon request or consent of the user or pursuant to subpoena, court order or where otherwise required by statute."
 What are examples of things to exclude? If a library is in shared space with a shared security surveillance system, that should be excluded (unless the library has confirmed via written contract that the footage of the library will only be reviewed per the policy). If the library has a snack bar or gift shop and wants to monitor the point of sale for theft, that could be excluded. Security footage of a community room used by third-party groups (not individuals) under a space rental agreement is another possible example.
 Even lawyers need to look this stuff up sometimes. Just like I don't have some of the finer points of the Domestic Relations Law at my fingertips, not all lawyers can recite the requirements of CPLR 4509.
 Or designated positions with regular training and/or adequate experience to appreciate the fine points of the library's policy.