The prohibition in N.H. Rev. Stat. § 359-N:2 shall not apply to biometric data collection practices implemented pursuant to statute or practice prior to the effective date of this section, provided that the government agency shall not subsequently expand or modify the type of data collected or the purpose for which it is collected without legislative approval. Legislative approval shall not be required for an airport to expand or modify its biometric collection and use practices if identified in the airport’s federally-mandated airport security program and approved by the U.S. Transportation Security Administration. Nothing in this chapter shall limit the collection of biometric evidence by law enforcement agencies at crime scenes or its examination and analysis by forensic laboratories. The admissibility at trials of biometric evidence and expert opinion based on such evidence shall be determined by the presiding judge within the parameters and limits specified in the rules of evidence.