Blood pressure is governed by five elements--the strength of the heartbeat, the volume of blood, the viscosity of the blood, the resistance of the arterioles, and the elasticity of the arterial walls. An abnormality of any of these can cause the blood pressure to be too high or too low.
Depending on the complexity of the case a trial can last anywhere from one day to six months or longer. If you are asking how long a rape prosecution takes you are probably looking at 6 months to a couple of years.
The trial lasts as long as it needs to. The trial's length depends on the number of witnesses and the questions asked them and the arguements ofthe lawyers and picking the jury and the court's instructions etc. This varies from case to case. In some cases a trial can go a day or two and in others weeks.