Revealed: Man who threw muck at Gerry Brownlee during Christchurch earthquake service is a sex offender

John Andrew Howland outside Christchurch District Court last month. Photo / Kurt Bayer

The man convicted of throwing muck over Minister Gerry Brownlee at a memorial service for victims of the Christchurch earthquake can today be revealed as a convicted sex offender.

John Andrew Howland, whose 14-year-old son, Jayden Andrews-Howland, was killed by falling masonry in the February 22, 2011 earthquake, tipped an ice cream container filled with "pretty mucky stuff" over Mr Brownlee's head at the five-year anniversary service last month.

Howland, 41, pleaded guilty to assault at Christchurch District Court and today was sentenced to 80 hours of community work.

Now it can be reported that Howland was sentenced to eight months' home detention in 2013 after being caught with thousands of images of child pornography on his computer.

Depression triggered by his teenage son's death - just a day before his 15th birthday - was behind his descent into the world of child pornography, Greymouth District Court heard.

His son, Jayden, was last seen boarding the No 3 bus into the Christchurch CBD shortly before the magnitude 6.3 quake on February 22, 2011, having been let out of school early because of a teacher-only afternoon.

Gerry Brownlee upset John Andrew Howland because he did not acknowledge the quake families. Photo / Kurt Bayer

Howland has previously said he targeted Mr Brownlee because the Government was "just heartless... no compassion".

"They're not taking care of all the [quake] families - like us, and everybody else," he said.

"There needs to be more support, more communication, and just compassion really."

He criticised Mr Brownlee for not acknowledging the families at the memorial service.

"He could've come over and said something but he didn't, he walked right past."

Howland prepared the mixture of flour, egg, vinegar, salt, pepper and cocoa at home before driving to Christchurch two days before the memorial. He thought about throwing it over Prime Minister John Key instead of Mr Brownlee. "If Brownlee wasn't there, I would've got Key," he said.

Police said that Howland's attack was pre-planned, with the unidentified brown sludge being prepared earlier in the week, police said.

He was sitting in the family members section at the memorial service held at the Botanic Gardens.

Killed in the quake: Jayden Andrews-Howland. Photo / Supplied

"Sitting a short distance away in the dignitaries section was the victim, Gerry Brownlee," the police summary of facts said.

"As the victim got up to leave, the defendant walked up to him with an ice cream container containing a brown sludge that he had prepared earlier in the week. The defendant poured the sludge over the top of the victim in a planned attack."

Howland later told police that he "didn't like" Mr Brownlee or the National Party.

In court today, Judge Gary MacAskill said Howland didn't act spontaneously and came prepared to be upset.