Children's author Helen Bailey could have been put in a martial arts neck lock while drugged and then suffocated, a court has heard.
The body of the successful 51-year-old writer was found alongside that of her beloved dachshund Boris submerged in "human excrement" deep below her lavish property in Royston, Hertfordshire, in July 2016, a jury at St Albans Crown Court was told.
Her fiance, Ian Stewart, 56, of Baldock Road, Royston, is accused of drugging and killing her, before dumping her body in a cesspit at the home they shared.
He denies charges of murder, preventing a lawful burial, fraud and three counts of perverting the cause of justice.
The court was told by Home Office pathologist Dr Nat Cary that, although there were no "obvious" signs of physical injury, the sedative Zopiclone was found in her system.
The sleep drug had been prescribed to Stewart, but hair analysis suggested it had been in Ms Bailey's system for several months, including at the time she died.
Although the cause of death was "undetermined", Dr Cary said a sedated Ms Bailey could have been killed without visual injuries by more "subtle" means.
He said: "Subtle modes of death include smothering and compression of the neck by means including an arm lock, using the crook of the elbow ... also called a sleeper hold, it is used in certain martial arts to reduce consciousness.
"That is another possibility to consider."
But on cross-examination by defence counsel Russell Flint QC, he said this was only speculation.
He added: "I am not (sure) but, on the basis of the case as a whole, it is my opinion that not only was she concealed by a third party but it seems likely she died at the hands of the third party by some means."
Jurors were told it was possible that Ms Bailey had consumed the drug unknowingly, but Dr Cary later said he could not know for sure.
It is alleged that the killing had "money as its driving motive", with Stewart in line to be a "substantial" benefactor of the author's £4 million fortune in the event of her death.
On Tuesday, the court heard that Ms Bailey had become concerned about feeling unnaturally sleepy in the weeks leading up to her death.
She used a search engine to look up terms including "can't stop falling asleep" and told her family she felt forgetful.
A statement from her mother, Eileen Bailey, read to the court said: "She would say 'Mum, I don't even recognise my own hands' when she was sitting at the computer."
Prosecutor Stuart Trimmer QC said: "The reason, the Crown says, is quite clearly because she was being fed Zopiclone."
Zopiclone was prescribed to Stewart for insomnia, which would have made Ms Bailey easy to kill "with little or no resistance", jurors were told on the opening day of the trial.
During a post-mortem examination, traces of the drug were found to have been in her body as early as February 2016.