Bradley Wallace, 24, assaulted Father Thomas White when he was unable to get back inside St Alphonsus Church on London Road, Glasgow, when hundreds of parishioners were leaving.
Police took the vestment worn by Father White at the time for forensic analysis.
Weeks later a DNA ‘hit’ matching Wallace was found with the saliva found on the back of his vestment.
Officers then found Wallace’s Facebook page with pictures of him holding up an England flat with a union jack flag in the corner, with the words “Bridgeton Loyal” emblazoned on the front.
Wallace, from Uddingston, South Lanarkshire, pled guilty at Glasgow Sheriff Court today to assaulting Father White on July 7, last year.
Sheriff Andrew Cubie told him “I want you to be under no illusion at all, spitting is disgusting and cowardly and this was done in the context of a sectarian atmosphere which is an embarrassment to the West of Scotland.
“You should be under no illusion all options are open to the court.”
Procurator fiscal depute Chris Farrell said on July 7, last year, was the annual Boyne Parade in Glasgow which had around 4,000 participants and attracted an equal amount of spectators.
Around 5pm the parade was on its return route having “splintered off into different factions” who took different routes through the city.
He said: “At this time one of the factions was walking along London Road towards its junction with Kent Street.
“They were flanked by a number of police officers who took position outside of St Alphonsus Chrch, due to it being a Catholic congregation.”
The court was told Father White had finished his Sunday mass and as is customary, was at the front entrance to say goodbye to his parishioners.
There were around 250 of them and while he stood on the pavement he could see the parade coming towards the church and tried to get back inside.
Mr Farrell added: “Due to the number of parishioners creating a bottleneck at the door he was unable to get back into the church.
“At this time the members of the public associating themselves with the parade began to sing sectarian songs and shout words Father White and the parishioners.
“This included terms such as ‘Fenian b*******’, ‘Fenian scum’, ‘beast’ and ‘paedophile’.”
A large scale disturbance broke out at the junction between the two streets which took police away from the church.
With no officers there, members of the public who had been associating themselves with the parade became more volatile towards the congregation.
It was heard that “a number of this group began to spit towards them” and Wallace, who was amongst the group, spat on Father White’s back.
A man holding a twirling baton began “prodding” this in the direction of Father White but did not touch him.
Police then returned and were told of what had happened. Father White did not want to divert resources away from the parade and said he would give a statement later.
He later gave one and police took the vestments he wore that day which were sent away for forensic analysis.
Mr Farrell said on July 9, 2018 Shettleston Criminal investigation department were tasked with progressing enquiries including CCTV trawls and online enquiries.
He added “On July 23, they were informed of a DNA hit matching Wallace’s profile held on the police DNA database.
“The saliva was found on the back of Father White’s vestments.
“The police continued to carry out open source checks and identified a Facebook page belonging to Wallace.
“This depicted images of him holding up an England flag with a Union Jack flag in the corner with he words ‘Bridgeton Loyal’ emblazoned on the front, alongside other images pertaining to the ‘Bridgeton Loyal Band’.”
He was contacted by police and agreed to go to London Road in the following days where he made no reply to caution and charge.
Wallace, represented by John Coogan, had his bail continued by the sheriff and will be sentenced later this month.