A 65-year-old woman and her son have been arrested after police suspected they were planning to take her husband to the Dignitas clinic in Switzerland to commit suicide.
The pensioner and the 25-year-old, from the Chichester area of West Sussex, were being held on suspicion of encouraging or assisting a suicide.
The woman and her son have been released on police bail until 8 October, following their arrest on 8 August. The condition of the 71-year-old man is not known and the family have not been identified by Sussex Police.
The force has confirmed they were having the mental capacity of the "vulnerable" man assessed to determine his ability to make decisions independently.
A Sussex Police spokesman said: "Police have been made aware of suggestions that a man and a woman from West Sussex could be planning to take a vulnerable pensioner to the Dignitas clinic in Switzerland so that he can end his life.
"Officers are currently having the mental capacity of the vulnerable 71-year-old reviewed to determine how able he is to make decisions for himself.
"A 25-year-old man and a 65-year-old woman from the Chichester area were arrested on Thursday, August 8, on suspicion of encouraging or assisting a suicide.
"Both have been released on bail without charge until 8 October while officers carry out further inquiries."
Whilst assisted suicide is legal in Switzerland, it is a criminal offence in the UK and carries a maximum sentence of 14 years imprisonment. Individual decisions on prosecution are now made on the basis of the circumstances in each case.
The Dignitas association was established in 1998 and offers anyone who has an incurable or unendurable illness an assisted suicide at their Swiss or German clinics.
Dignitas has assisted over 150 British suicides since it opened 15 years ago.