Legal transcription is a specialized form of transcription that involves transcribing legal audio/video to text format. As is very obvious from the term, legal transcription involves an audio that is of legal nature and thus includes legal terminology which in many cases, might not be understandable by the lay man. Also, needless to say, in a legal content, a slight terminology error here and there can actually be a blunder leading to a complete misinterpretation of the transcribed text.
Thus, to get the stuff transcribed effectively and accurately for a legal audio, experts with rich legal experience are needed. Let us take it in this way – a person who is not aware of legal terminology can probably listen to the words and take them down but because he does not understand them and cannot relate to them, so he cannot transcribe them with accuracy and take down audio in a way that the entire transcribed text makes as much sense as the spoken audio. As such, for professional legal transcription services, a transcription agency must have transcribers on board who are experts in this domain (may be lawyers, magistrates etc).
In a nutshell, legal transcription is a specialized form of transcription and must only be handled by masters in the trade!