The Court of Appeal is due to rule on the case of a paralysed man who wants to be helped to die.
The family of late locked-in syndrome sufferer Tony Nicklinson and paralysed road accident victim Paul Lamb have lost their right-to-die challenges.
Paul Lamb wants the law changed so he can kill himself with a doctor's help.
The Court of Appeal upheld a High Court judgement in the case of the late Mr Nicklinson, ruling he did not have the right to ask a doctor to end his life.
Mr Lamb, 57, from Leeds, has been almost completely paralysed from the neck down since a car accident 23 years ago and says he is in constant pain.
His widow, Jane, said she planned to appeal to the Supreme Court.
Unable to end his own life, he wants a court ruling that any doctor who helped him die would have a defence against the charge of murder.
Mr Lamb has said he wanted the law changed so he could kill himself with a doctor's help.
The defence - known as "necessity" - would be that it had been necessary for the doctor to act to stop intolerable suffering.
Jane Nicklinson told the BBC she was "very, very disappointed" by the ruling, but "not totally surprised".
This is the same argument put forward by another paralysed man, Tony Nicklinson, who died shortly after his case was rejected by the High Court last year.
"They are not going to get rid of us that easily," she said, as she explained she would be seeking permission to appeal to the Supreme Court.
Mr Nicklinson's widow, Jane, is challenging that ruling, which stated that it was for Parliament, not judges to decide whether the law on assisted dying should change.
She added that it was a very complicated legal matter.
"What we are hoping for is that people like Tony that find themselves in such a terrible situation, as Paul Lamb does, that when they feel they have had enough that a doctor can take their life for them because they are unable to do it themselves," she told BBC's Breakfast programme.
"Although we lost, the legal team are quite pleased with the outcome - the appeal judges actually upheld a couple of points which the High Court rejected, which is a step forward."
The Appeal Court will also rule on the case of another paralysed man, known only as Martin, who wants the Director of Public Prosecutions to change his policy on suicide. Martin wants it to be lawful for a doctor or nurse to help him travel abroad to die with the help of a suicide organisation in Switzerland.
Mr Nicklinson died naturally at his home in Wiltshire last year.
At the beginning of the appeal, the lord chief justice said that despite the desperate situation of those involved, the case had to be decided on the basis of principles of law rather than as a matter of sympathy.
Mr Lamb has no function in any of his limbs apart from a little movement in his right hand. He says he has been in pain for 23 years, needs 24-hour care and his life consists of "being fed and watered".
In a statement to the courts, he said: "I am in pain every single hour of every single day. I have lived with these conditions for a lot of years and have given it my best shot.
"Now I feel worn out and I am genuinely fed up with my life. I feel I cannot and do not want to keep living. I feel trapped by the situation and have no way out.
"I am fed up of going through the motions of life rather than living it. I feel enough is enough."
Mr Lamb, a divorced father of two, said he was not depressed and just wanted to end his life in a dignified way, with his loved ones around him.
Jane Nicklinson, whose husband Tony had "locked-in" syndrome, said: "Everyone has different expectations for life.
"Tony couldn't cope with life like it. Every day waking up was torture for him."
Father-of-two Mr Nicklinson, 58, refused food and contracted pneumonia after the courts decided he could not end his life at a time of his choosing with the help of a doctor. He died a week later.
Labour peer Lord Falconer said if the Court of Appeal judges backed doctors killing someone who wanted to die, they would in effect have to change the law by changing the "ingredients and defences of murder".
This, he said, was "very unlikely".
"I think the law has got to draw the line against allowing people to be, in effect, killed by doctors when they have not got any reduction in life expectancy," added Lord Falconer, who has previously tabled a private members' Bill to try to legalise assisted suicide for the terminally ill in England and Wales.
