The purpose of an introduction
In giving an introduction (exordium) at all, there is no other object but to prepare the hearer to listen to us more readily in the subsequent parts of our pleading. This object, as is agreed among most authors, is principally effected by three means: by securing his good will and his attention, and by rendering him desirous of further information.
Quintilian
The introduction of a speech usually announces the subject, legal issues and purpose of the case. However, a fundamental objective of the introduction (whether written or spoken) is to establish the personal and professional credibility of the advocate to the court, which the classical rhetoricians called ethos. This needs to be done first: if it isn’t the advocate won’t be persuasive.
Quintilian identified the introduction as “that part of the speech addressed to the judge before he has begun to consider the actual case. The purpose is to “prepare our audience in such a way that they will be disposed to lend a ready ear to the rest of our speech.” This is accomplished by including “the points which seem most likely to serve our purpose” and by rebutting or lessening the force of points that damage our case.”
Cicero states that the purpose of the introduction is to secure “an intelligent and an attentive hearing, by starting with the facts themselves”. The purpose of the introduction “is to enable us to have hearers who are attentive, receptive and well-disposed.”
Thus, the purpose of the introduction is to make your audience receptive and emotionally engaged with the case and hopefully get the judge onside. The rhetoricians suggest you write or speak as an emotionally invested advocate, using a temperate or low-key delivery, as your primary aim is to establish your credibility and give the court a good idea of what the case is about. As the aim is to instruct, you should use plain and simple language generally. However, another aim is to please the court, so chucking in the odd elegant turn of phrase or demonstrating your clear grasp of the issues in the case will hopefully help in establishing your personal and professional credibility.
Each introduction is individual and directly relevant to the facts, so avoid recycling them.Quintilian covers in detail how to write a good introduction (exordium) here.