Severely disabled Paul Lamb has arrived at the Court of Appeal in a bid to change laws governing the right to die.
Mr Lamb, 58, has been paralysed from the neck down since a car accident in 1990.
He is taking up a case begun by the late Tony Nicklinson, who appealed for the laws to change after suffering from "locked-in" syndrome.
Mr Nicklinson's widow Jane accompanied Mr Lamb and his daughter Lauren to court.
Paul Lamb's lawyer Saimo Chahal, who also represents the Nicklinson family said there is a "fundamental misunderstanding" about Paul's fight. She said:
If Paul did win the right, the cases would have to be on a case by case basis, so it wouldn't be a matter of vulnerable people suffering.
Dr Peter Saunders, from Care Not Killing, a UK based organisation which promotes care and opposes euthanasia said Paul Lamb is seeking a "very radical change in the law."
He said: "If he was successful in getting that legal change it would drive a coach and horses through not the suicide act but the murder act as well and that would put a lot of vulnerable, elderly people at risk
"The proper place to be making this decision is not in court, it's in Parliament", he added.
A challenge by a third man, whose case was rejected at the High Court on the same day as Mr Nicklinson's, will also be heard today.
The locked-in syndrome sufferer, who cannot be identified for legal reasons but is referred to as "Martin", suffered a massive stroke in August 2008.
He is unable to speak and virtually unable to move, describing his life as "undignified, distressing and intolerable", and wants to be allowed a "dignified suicide".
The case of paralysed road accident victim Paul Lamb, who won the right to join the litigation to continue the battle started by Mr Nicklinson, will also be considered during the appeal court hearing, which will last several days.
Immobile except for limited movement in his right hand, Mr Lamb has been in significant pain since the 1990 tragedy.
The former builder and father-of-two said in a statement after winning the right to have his case heard: "I hope that this is the next step towards the ultimate goal of changing this cruel law, which keeps people like me alive when I want to have a dignified death.
"To be given this chance of being involved in the case makes me very proud. I have always been an extremely strong character and when I believe in something, I can take on the world.
"So, for the sake of everyone in this country who deserves the right to have a dignified death, I hope that we can make this happen."
The family of Tony Nicklinson will continue to challenge the High Court ruling against doctor-assisted death today.
Mr Nicklinson's widow, Jane, has been joined in her fight by Paul Lamb, 58, from Leeds, who is paralysed.
"We are really excited that we are back in court and hopeful that we will win the appeal and have the case heard again," Jane said yesterday.
"We are hoping that the judges will see that we didn't get a fair hearing last time and that we should get the case heard again. We feel that our case wasn't properly heard."
Paralysed Paul Lamb and the family of the late Tony Nicklinson will appeal their unsuccessful challenges on the illegality of assisted suicide at the High Court.
The Lord Chief Justice, Lord Judge, and two other judges will hear the challenges today in the Court of Appeal.
Mr Nicklinson, 58, who suffered from locked-in syndrome, died on August 22 last year days after losing a landmark High Court right-to-die case.
Fifty-eight-year-old Paul Lamb, from Leeds, has joined forces with the family of Mr Nicklinson, who died in 2012, severely injured in a car accident in 1990, Mr Lamb no function in any of his limbs apart from a little movement in his right hand.