Alan Power, who has been a member of a Spiritualist church for 30 years, argues that his belief in the power of mediums should be placed on a par with more mainstream religious and philosophical convictions.
He has already secured a legal ruling that his principles are covered by laws designed to prevent religious discrimination in the workplace, and is now seeking to prove that they were the reason for his dismissal.
Mr Power's case follows a landmark ruling last month that environmental views should be considered equivalent to religious and philosophical beliefs, following a legal challenge by a green executive at a property firm.
At a tribunal in London, Mr Power will claim that Greater Manchester Police broke the law by sacking him for believing that mediums should be consulted in criminal investigations.
In an initial judgement seen by The Independent, Judge Peter Russell said that the case had merit because his Spiritualist views "have sufficient cogency, seriousness, cohesion and importance" to be covered by the Employment Equality (Religion or Belief) Regulations 2003.
The judge wrote: "I am satisfied that the claimant's beliefs that there is life after death and that the dead can be contacted through mediums are worthy of respect in a democratic society."
Mr Power's former employers are expected to argue that Judge Russell's ruling was not justified, and highlight that the trainer did not initially claim that his belief in the usefulness of psychics to police investigations amounted to a religious conviction.
A spokesman for Greater Manchester Police said: "GMP can confirm that a member of police staff was dismissed from his role as a trainer. The former staff member has appealed this dismissal. As the appeals process is underway it would be inappropriate to comment further."
Last week it was disclosed that police in Wales spent £20,000 following up murder case "leads" supplied by a group of psychics.