The victim was identified as 25-year-old Dustin Calley.
The crash happened on Thursday morning along Pine Street near Howard Road. Officers said Chaffin was making a left turn when he hit Calley on his motorcycle.
The victim was rushed to Madera Community Hospital where he later died.
"Someone not being under the influence may have very well have seen him and not turned in front of him. It's tragic on so many levels," Sgt. Thomas Burns said.
This is the first pot-related DUI that's ended with someone dead in the City of Madera. Burns said the driver told officers he didn't see Calley. He said a series of tests made it clear that Chaffin was under the influence.
"If you're intoxicated, you can't control what your eyes do, but they will give certain responses to certain things based on what's in your system. (Chaffin) indicated he was certainly under the influence of marijuana," Burns said.
Calley's fiancé said he was on the way to work at the time of the accident. She also said he cared about others and cared about his community, and that he had his whole life ahead of him.
Now that recreational marijuana is legal, officers fear that there will be more of these incidents. California Highway Patrol officers say along with field sobriety tests, they also do a drug recognition evaluation.
"There's a clinical component to it as far as blood pressure tests, there's evaluation of pupil sizes, different clinical indicators, different signs of ingestion you may see under the influence of drugs," Lt. Gil Peirsol said.
However, there are still several gray areas when it comes time to prosecute.
"If you're over a .08 the law has deemed you to be under the influence (of alcohol), we don't have that for marijuana," Peirsol said.
Chaffin was arrested and charged with vehicular manslaughter. Police said that Chaffin admitted to officers that he used marijuana for medical reasons, but that he hadn't taken any at the time of the accident.
Officers said the police report would be sent to the Madera County District Attorney's office on Tuesday.
Calley leaves behind a daughter and two sons. He was also an Army veteran.
Chowchilla Volunteer Fire Department is holding a "Fill the Boot" fundraiser for Calley's family. They will be collecting donations on Sunday May 27th, from Noon to 4:00 pm at the Chowchilla Shell Station located at 105 North Chowchilla Blvd. Donations will also be accepted at any time at the Chowchilla Fire Station located at 240 North First Street.