A Jamaican disciplinary panel on Thursday banned former 100-meter world record holder Asafa Powell from athletics for 18 months after the veteran sprinter tested positive for a banned stimulant last June.

In the sprinting powerhouse's capital of Kingston, the head of the three-member panel of the Jamaica Anti-Doping Commission said its decision was unanimous after examining the "voluminous nature of the evidence."

"In all the circumstances, Mr. Powell was found to be negligent, and he was at fault," said commission chairman Lennox Gayle, adding the panel would issue a written statement explaining its decision in about a month.

'I have never knowingly taken any banned substances, I did all the necessary checks before taking Epiphany D1 and it is my hope that the CAS will prove to be a more open and fair avenue for the review of all the facts in my case'- Asafa Powell

Powell's backdated ban begins from the date of his sample collection on June 21, 2013 during national trials for the world championships. That means he's eligible to return to competition on Dec. 20, about a month after he turns 32.

Once the top sprinter on the track, Powell lowered the world record in the 100 to 9.77 in 2005, then 9.74 in 2008 before being eclipsed by countryman Usain Bolt. Powell was the Jamaican athlete who first put Jamaica's dominating athletics prowess on centre stage in the 21st century. But unlike Bolt, he could never win the big one.

The 31-year-old sprinter tested positive for the banned stimulant oxilofrone at Jamaica's national trials last June. He'd been suspended from competition since his doping case was disclosed in July.

Powell did not attend the Thursday session, but he issued a statement through his publicist saying his defence team will appeal to the Court of Arbitration for Sport. He described the ruling as "not only unfair, it is patently unjust."

Like former teammate Sherone Simpson, a three-time Olympic medallist who tested positive for the same stimulant at the national trials in June, Powell placed the blame on a newly-hired trainer who provided the two athletes with supplements, including one called "Epiphany D1" which lab tests later showed to contain oxilofrone.

"I have never knowingly taken any banned substances, I did all the necessary checks before taking Epiphany D1 and it is my hope that the CAS will prove to be a more open and fair avenue for the review of all the facts in my case," Powell said in his Thursday statement.

During hearings earlier this year, Powell testified that he received nine supplements from Canadian physiotherapist Christopher Xuereb, including Epiphany D1. Powell said he started taking the capsules in early June after he and a friend researched the supplement for up to six hours online and found no prohibited substances.

But Xuereb has said he never gave Powell or Simpson any performance-enhancing drugs and only purchased major brand vitamins. In July, he asserted to The Associated Press that both athletes were looking for a scapegoat. Xuereb once worked at the Toronto clinic run by Anthony Galea, a sports physician who pleaded guilty to bringing unapproved and mislabeled drugs into the U.S. for house calls.

On the morning of the Jamaican trials, Powell said he took four capsules of Epiphany D1 at Xuereb's suggestion after previously taking two each morning. Powell ended up finishing in seventh place and failed to qualify for the world championships.

The sprinter, who turned professional in 2002, raised eyebrows during his testimony in January when he said he wasn't acquainted with doping control rules. He also testified that he did not tell a doping control officer about all the new supplements he'd been ingesting, only listing three on his declaration form, because he couldn't remember their names amid the excitement of the Jamaican trials.

On Tuesday, Powell's former teammate Simpson was also banned until Dec. 20 after testing positive for oxilofrone. Her 18-month ban also began from the sample collection date at Jamaica's national trials. She will appeal to the Court of Arbitration for Sport (CAS). The two athletes, both represented by agent Paul Doyle, delivered nearly identical defences.

The Jamaican disciplinary panel on Tuesday also issued a two-year ban for Olympic discus thrower Allison Randall, who is suspended until June 2015.

Earlier this year, sprinter Veronica Campbell-Brown was cleared of doping on appeal by CAS after testing positive for a banned diuretic at a Jamaican meet. The full reasons for the three-time Olympic gold medallist 's exoneration have not yet been released, but CAS said the ruling was based on faulty sample collection.

Powell has won four world championship medals in his career, including gold in the relay in 2009.

Only two men have run faster than Powell at 100 metres: Bolt and Tyson Gay.

The American Gay also tested positive for a banned substance last year, although the U.S. Anti-Doping Agency hasn't yet ruled on the matter.

With files from CBCSports.ca