A 65-year-old woman and 25-year-old man have been arrested after police were warned they could be planning to take a "vulnerable" pensioner to end his life in Switzerland.
The pair were held by officers in West Sussex who are now investigating the mental capacity of the 71-year-old to determine how able he is to make decisions for himself.
The woman and man, reported to be mother and son, were questioned on suspicion of encouraging or assisting a suicide.
Their names have not been released by police but they are believed to be from Chichester.
A Sussex Police spokesman said: "Both have been released on bail without charge until 8 October while officers carry out further inquiries."
The charity Dignity in Dying told Sky News they were not aware of the family and had not been in contact with them.
However a spokesperson said: "Sad cases like these highlight why a robust assisted dying law with upfront safeguards would far better protect everyone than the current situation does."
It is an offence to encourage or assist suicide under the Coroners and Justice Act 2009 and officers are investigating whether any crime has been committed or is likely to be committed if they do not take action.
In February 2010 the director of Public Prosecutions Keir Starmer QC released guidance to prosecutors in relation to cases of encouraging or assisting suicide.
It was indicated that anyone acting with compassion to help end the life of someone who has decided they cannot go on would be unlikely to face criminal charges.
Assisted suicide remains a criminal offence in England and Wales, punishable by up to 14 years in prison, but individual decisions on prosecution are now made on the circumstances in each case.
Mr Starmer said at the time: "The policy is now more focused on the motivation of the suspect rather than the characteristics of the victim. The policy does not change the law on assisted suicide. It does not open the door for euthanasia. It does not override the will of Parliament. What it does is to provide a clear framework for prosecutors to decide which cases should proceed to court and which should not.
"Assessing whether a case should go to court is not simply a question of adding up the public interest factors for and against prosecution and seeing which has the greater number. It is not a tick box exercise. Each case has to be considered on its own facts and merits.
"As a result of the consultation exercise there have been changes to the policy. But that does not mean prosecutions are more or less likely. The policy has not been relaxed or tightened but there has been a change of focus."
There have been a number of high profile cases of Britons going to Switzerland to end their lives.
The parents of paralysed rugby player Daniel James, 23, did not face charges after attending the Dignitas clinic with their son in 2008.
In 2009 conductor Sir Edward Downes and his wife Lady Joan chose to die together at the clinic rather than struggle on with health problems.
:: Anyone feeling emotionally distressed or suicidal can call Samaritans for help on 08457 90 90 90 or email jo@samaritans.org.
