It can have several possible meanings.
It sounds like a legal request for the forensic chemist/technician who analyzed the evidence OR perhaps a request for the results of the forensic exam itself to be present at trial as a witness. (???)
More would have to be known about the context in which this phrase appears in order to attempt a more precise answer.
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Such a phrase can have many possible meanings and more would have to be known about the origin of the phrase (i.e.: court document? - etc?) in order to attempt an answer.