Blood drops on a 3-foot-tall marijuana plant inside an Agate greenhouse provided a clue that helped close a homicide case in which the victim was found 100 miles away in the trunk of a burned-up car.

The DNA from the blood linked the legal grow operation to the charred remains of Jason Michael Dosa, 44.

The body was discovered Sept. 20 in the trunk of a Nissan Maxima after firefighters extinguished the car fire in a ditch on South Cougar Road in Jefferson County.

Now it appears that Dosa, who has been involved in various marijuana grow operations with two men, may have been harvesting pot when he was fatally shot.

One of those former pot partners, Shawn Edward Geerdes, 46, has been charged with first-degree murder in Dosa’s death. The name of the third partner was redacted from recently unsealed court records.

Along with murder, Geerdes also faces a charge of cultivating 30 or more marijuana plants, according to Elbert County District Court records.

Geerdes was originally charged in Jefferson County but that case was dropped when investigators determined the fatal shooting likely happened near Agate.

At 2:45 a.m. on Sept. 20, Dosa left his home carrying a box and tree-trimming loppers. He told relatives that he was going to make between $20,000 and $30,000. He was wearing a gray, hooded Under Armour sweat shirt.

A man living near Agate couldn’t sleep and went out to his porch to smoke. Suddenly, he heard about 10 gunshots coming from his neighbor’s house between 2:30 a.m. and 4 a.m. Geerdes’ house is across the street.

“It wasn’t a bang, it was a pop,” the man was quoted as telling investigators. The gunshots were followed by about 15 minutes of silence. Then he saw someone walking with a flashlight in front of Geerdes’ house, according to records.

An autopsy on Sept. 21 revealed five bullets in Dosa’s body, two in his chest, one in his jaw and two in his legs.

Jefferson County investigators determined that Dosa’s cellphone had pinged off a cell phone tower in Agate at 9:22 a.m. At 11:24 a.m., the cellphone pinged off a tower a mile away from the location where his body was found.

According to the court records, Dosa and Geerdes had entered a partnership in a marijuana grow operation at Geerdes’ place, 36995 County Road 162 in Agate.

Under the agreement, Dosa and the third partner would build a greenhouse for the marijuana operation in exchange for a share of the marijuana harvest, court documents show. But the deal broke down.

Dosa, who filed for bankruptcy in July, lost a “substantial” amount of money in the deal and was very angry about it, according to the unnamed partner.

Two days before his death, Geerdes showed Dosa and the other partner the 35 mature marijuana plants in the greenhouse.

“Jason was impressed with the size and quality of the marijuana plants,” the third partner told investigators.

When the third partner met Geerdes the afternoon of the day Dosa’s body was found, he asked Geerdes how he had gotten a fat lower lip.

Geerdes had replied that he had gone to Denver, gotten ecstasy and had sex with a girl and the girl’s boyfriend caught them and hit him, the documents say.

Two days after Dosa’s murder, Jefferson county investigators searched Geerdes’ home and the greenhouse.

They found blood drops on a marijuana plant, gravel on the floor and on the east wall.

Investigators found two .22-caliber shell casings on the floor as well. Dosa was killed with what technicians believed were .22-caliber bullets. They found a box of high velocity, hollow-point, .22-caliber American Eagle bullets in a crawl space above Geerdes’ kitchen.

Kirk Mitchell: 303-954-1206, kmitchell@denverpost.com or @kirkmitchell or denverpost.com