Studies have shown 80%-90% of jurors make their minds up after opening statement.
Since a large number of jurors make up their mind after opening statement there should be a presumption against holding back during opening statement. Some attorneys hold back during opening to gain flexibility or the element of surprise. But if the jury has already made up their mind it can be very difficult to change it.
PRIMACY
People tend to remember the first thing they're told. This concept is known as primacy, and it is also when most people make up their mind. For this reason the primary goal of opening statements will be to persuade the jury to your theory of the case (In closing it will be to motivate the jury). After opening statement many of the jurors will likely be looking for evidence that confirms their opinion. This is called confirmation bias.
ARGUING IN OPENING STATEMENT
Although not allowed by the rules judges generally permit some amount arguing in opening statement. Simple inferences in opening statements will generally be allowed. In my experience the chances of opposing counsel objecting to these types of arguments in opening statements have been low, and when attorneys do object judges will usually overrule the objection. When defending a case, if you use The Defense Four-Step Opening Statement this is usually not be a problem.
