The most serious allegations arose on February 27 when Mr Crichton was told by a colleague that other staff were taking drugs at work. He phoned Mr Tweeddale two days later about the drugs, asking the information to be treated confidentially.
Mr Tweeddale denied the confidentiality agreement, and told his foreman everyone should be tested.
The foreman called a meeting, and told everyone that drug testing would take place because Mr Crichton had reported the alleged drug use, something Mr Crichton said caused him extreme concern. Both he and the colleague who told him about the drug taking (called "M" in the authority decision) were told they were being tested after the meeting. Mr Crichton thought he was being targeted, but was more worried about the fact M failed his test but was able to go back to work.
M accepted that was the case, telling the authority his result "was swept under the carpet".
Mr Crichton left work after being allegedly confronted by Mr Tweeddale in front of five fellow employees, and accused of causing a "big ****** rift here".
"I had raised a serious concern and it could have impacted on [co-workers'] incomes, so from their perspective I had crossed them," Mr Crichton said.
While the company did not appear at the authority meeting, in a letter it denied Mr Crichton's claims. The letter contained statements signed by staff, including one from M.
But M told the authority the statements were pre-prepared and presented by the foreman, who demanded they be signed. M signed because he thought he might be out of a job if he did not.
Authority member Michael Loftus said he found Mr Crichton to be a credible witness, backed up by M's "unsolicited admissions of criminal activity."
Mr Loftus said TD had a duty to provide Mr Crichton a safe workplace, and not doing so can amount to a constructive dismissal.
He said revealing Mr Crichton as the source of the drug revelations put him in a dangerous position, and almost nothing was done to address his concerns.