John Stephen Green, 65, was said to be unable to wait any longer for his 88-year-old mother Bernadette to die so he murdered her.
The elderly woman's emaciated body was found at their family home in Aston-in-Ribble in May.
The Crown say his motive for the alleged killing was revealed in a series of text messages he sent to his daughter in the months leading up to Mrs Green's death on May 18.
Green "dehumanised" his mother, referring to her as "it" and and the month before stated he was looking after a "stinking corpse", jurors at Preston Crown Court were told.
Francis McEntee, prosecuting, said the defendant had lived with his mother at his former childhood home in Inkerman Street since 2009 after the failure of his marriage.
Neighbours thought they enjoyed a normal mother and son relationship as Mrs Green came increasingly to rely upon her son after she was taken to hospital in 2009 after a fall on the stairs.
The prosecutor said: "The defendant appeared to be a caring and attentive son.
"However, in the messages sent to his daughter towards the end of his mother's life, he claimed he felt trapped in a life that he regarded as a 'crock of crap' - tending to a woman he regarded not as his mother but as a burden whose lingering existence was ruining his life."
Jurors were read a selection of the messages, which the Crown say showed a common thread of "vitriol" and Green's belief he could only be free after his mother died.
In November 2016, Green wrote: "This is effing mental. When does it die? It's orribubble."
The following February, he said: "I hate her. I really, really hate her."
In March 2017, he texted: "Still alive. How do I holiday? She's wrecked, hate her but I'm stuck with responsibility. One day eh?"
On New Year's Eve that year, he wrote: "Just told the cow what she is."
In April this year, Green wrote: "Ain't that just typical? Sod's law. I've got out for a short while, I'm looking after a stinking corpse. Hey ho."
Just five days before Mrs Green's death, he texted: "Been a grim and gruesome five weeks here. Last two weeks horrendous, she's at death's door but nobody's opening it. Shouldn't be allowed."
Mr McEntee said the defendant later characterised the text exchanges as "dark humour" and indicated he was "just venting his spleen".
He added: "The prosecution say the sentiments expressed in those messages were certainly dark but they were in no sense humorous.
"We will invite you to conclude that his repetition in expressing such views, displaying anger - and you may think hatred - toward his mother reveals his underlying resentment for the position in which he professed himself trapped."
Green rang emergency services on the evening of May 18 and told an operator that attempts at resuscitation would be pointless as he was certain she was already dead, the court heard.
Mrs Green's body was found under dirty bedding within a "generally cluttered and dirty room", which Green explained was due to self-neglect by his mother who he said had given up on life following the death of his father.
Her death was referred to the coroner after it emerged she had not been seen by a doctor since October 2013.
A post-mortem examination revealed the body of an "emaciated female who had been the subject of severe neglect" with the "most readily apparent features" being an extensive area of black dead tissue around her buttocks.
Mr McEntee said the "clear evidence" from the Home Office pathologist was that Mrs Green died as a result of having been smothered.
The autopsy revealed no natural disease to cause or accelerate death, or to cause collapse, he said.
The prosecutor said he understood it was the defendant's case that he simply did nothing to harm his mother.
Green, an ex-officer with Lancashire Constabulary, denies murder.
The trial, scheduled to last up to six days, continues today.