The first is the Frye Test
According to the Frye Test, which is also known as the Frye Standard, an expert witness testimony is valid if the techniques used in providing the testimony have been generally accepted by the scientific community as a valid technique in the field of study that is in question. Many courts abandoned this standard but some still stick to it
The second is the Daubert Standard
This standard is more complex as it has many more things on the checklist of reliability. For starters, the Judge is the gatekeeper who decides whether or not something is reliable. Also, scientific knowledge presented must have been proven through a scientific method in a manner such that the results are relevant and reliable. It was created because it was believed that the Frye standard was not reliable enough to be used in a court.
The third is the Reliability standard
This standard also came into existence out of the problems that existed with the Frye standard. It focuses on reliability while abandoning many of the Frye test principles. It is often used together with Frye as it is believed that it updates the Frye standard while abandoning its negative aspects. Compared to Daubert it is less comprehensive.