Employees do not need to actually be disabled to be protected against discrimination on grounds of disability under equality laws (the Equality Act 2010 in GB or the Disability Discrimination Act 1995 in NI). Employees can be protected because they are associated with a disability (e.g. they are the parent of a disabled child) or, as in this case, they are perceived to have a disability or a progressive condition that, whilst not currently meeting the definition of a disability, could go on to become a disability over time.

The claimant in this case was a serving police officer, and was refused a transfer from Wiltshire to Norfolk when she did not meet the Police National Recruitment Standards relating to hearing. She was marginally outside the limit for the force (she suffers from bilateral mild sensori-neural hearing loss with tinnitus) but, crucially, had performed well in her role before applying for a transfer.

The Acting Chief Inspector (ACI) responsible for transfers had concerns that officer Coffey's hearing could deteriorate. Perhaps not to the extent that she was disabled but to the extent that she might need to be placed  on restricted duties - at least potentially, a "non-disabled permanently restricted officer". The ACI did not want to increase the pool of officers on restricted duties.

So, the ACI did not believe the claimant was disabled within the meaning of the Equality Act. However, her beliefs are not what count, according to the EAT. The legislation has provision for progressive conditions and the ACI clearly believed the claimant had such a progressive condition. The ACI's erroneous understanding of the law is neither here nor there. The condition was therefore covered by protections under the Equality Act and, since she was treated differently to a non-disabled person who had performed well but did not have a progressive condition, she was directly discriminated against on grounds of her disability.

As Judge Richardson concluded in the EAT's decision:

"I would add that I see no reason to doubt that the European Court of Justice would recognise direct discrimination on the grounds of perceived disability. The ECJ has now consistently said that the Equality Directive, along with the linked Racial Discrimination Directive 2000/43/EC, is not to be interpreted restrictively and is to apply to persons who suffer less favourable treatment or particular disadvantage by virtue of a prohibited characteristic even if those persons do not themselves have the protected characteristic: see the associative discrimination case of Coleman v Attridge Law [2008] IRLR 722 applied more recently in an indirect discrimination case, Chez Razpredelenie Bulgaria AD v Komisia Za Zashtita Ot Diskriminatsia [2015] IRLR 746..."

So, notwithstanding that NI employees might have to rely on CJEU jurisprudence in the absence of explicit cover in domestic legislation, similar protections on perceived disability should apply in Northern Ireland.
http://www.bailii.org/uk/cases/UKEAT/2017/0260_16_1912.html