This briefing firstly sets out the definition of terminal illness in the Assisted Dying for Terminally Ill Adults (Scotland) Bill. It then explores other definitions of terminal illness as set out in existing or proposed legislation in the UK and overseas.
Section 2 of the Assisted Dying for Terminally Ill Adults (Scotland) Bill defines terminal illness, for the purposes of the Bill, as:
a person is terminally ill if they have an advanced and progressive disease, illness or condition from which they are unable to recover and that can reasonably be expected to cause their premature death1.
The policy memorandum that accompanies the Bill states that the member “decided that assisted dying for people in the end stages of life is most appropriate for the Bill”2. It further states that:
It is not the intention that people suffering from a progressive disease/illness/condition which is not at an advanced stage but may be expected to cause their death (but which they may live with for many months/years) would be able to access assisted dying2.
The Bill does not define terminally ill by reference to a period of life expectancy or prognostic timeframe. However, the policy memorandum states that the definition requires a person to be in an advanced stage of terminal illness (i.e. close to death). It further states that the Member in charge of the Bill thought that including an expected life expectancy within the definition could place unreasonable pressure on healthcare professionals and could result in excluding some terminally ill people from the process inappropriately2.
Section 23 of the Bill refers to guidance that the Scottish Ministers may prepare and publish "with regard to the lawful provision to terminally ill adults of assistance to end their own lives under this Act1.” This includes assessment of a terminally ill adult’s eligibility to be lawfully provided with assistance to end their own life. This is similar, but not identical to, provisions in Scottish social security legislation whereby the Chief Medical Officer must prepare and publish guidance relating to the definition.
Different definitions are used to determine eligibility for disability benefits under terminal illness rules in Scotland and the rest of the UK.
Under the Social Security (Scotland) Act 2018 a person is considered to have a terminal illness if they have "a progressive disease that can reasonably be expected to cause the individual's death"1. This definition moved away from prognostic timescales and allows registered medical practitioners and registered nurses to use their clinical judgement.
The Act specifies that the Chief Medical Officer must prepare and publish guidance that sets out when a progressive disease can reasonably be expected to cause an individual's death for the purpose of determining entitlement to disability assistance.
The Chief Medical Officer's guidance2 was developed with the help of healthcare professions – as stipulated in the legislation - and third sector organisations with an interest in this area. The guidance is intended to support clinicians to interpret and apply the definition consistently and sets out that it is a legal requirement for eligible clinicians to pay regard to this guidance when making their clinical judgement.
The guidance states that:
To meet the definition the individual should have an illness:
that is advanced and progressive or with risk of sudden death, AND;
that is not amenable to curative treatment, or treatment is refused or declined by the patient for any reason, AND;
that is leading to an increased need for additional care and support2.
The guidance also contains a range of information to help facilitate clinical decision making including:
criteria to be considered (sections 7, 8 and 9 in the guidance),
detailed condition specific indicators and tools (Annex B in the guidance),
several worked examples, (Annex C in the guidance) and
practical information relating to the new process (Annex A in the guidance). The benefits form asks clinicians to evidence the indicators that supported their clinical judgement in assessing eligibility.
Stakeholders involved in the development of the social security guidance gave evidence to the Health, Social Care and Sport Committee4 on their experiences of applying the guidance during Stage 1 scrutiny of the Assisted Dying for Terminally Ill Adults (Scotland) Bill. Mark Hazelwood, from the Scottish Partnership for Palliative Care told the Committee:
When Social Security Scotland was being established, I was asked by the office of the chief medical officer to chair a group that was trying to put together guidance to support the brief legal definition of terminal illness that was in the Social Security (Scotland) Bill. We found that it was very difficult to take vague terms such as “advanced and progressive” disease or “premature” mortality and to apply them precisely in practice.4
It should be noted that these stakeholders did not call for the introduction of a prognostic timeframe and referenced the difficulties for clinicians in providing a clear prognosis. This was a theme often discussed during the Committee’s Stage 1 evidence on the Assisted Dying for Terminally Ill Adults (Scotland) Bill.
It should also be noted that the purpose of the definition in the 2018 Act was intended to widen access to disability benefits for those living with terminal illnesses. It does not include a prognostic timescale, as it was determined that for many terminal illnesses, particularly non-cancer conditions like motor neurone disease (MND), chronic heart failure or chronic obstructive pulmonary disease (COPD), accurate prognosis can be difficult because of the unpredictable trajectories of the conditions.
By comparison, the UK Social Security (Special Rules for End of Life) Act 20226 used by the UK Department of Work and Pensions (DWP), sets out that a person is deemed terminally ill for the purpose of accessing disability assistance if they have “a progressive disease and their death as a consequence of that disease can be reasonably expected within twelve months”.
Different definitions have been used to determine eligibility for accessing assisted dying across the UK, Crown Dependencies, and in other jurisdictions. This section explores these definitions.
Kim Leadbeater MP introduced the Terminally Ill Adults (End of Life) Bill1 in the House of Commons in November 2024. The Bill, as introduced, defined someone as terminally ill if:
(a) the person has an inevitably progressive illness, disease or medical condition which cannot be reversed by treatment, and (b) the person's death in consequence of that illness, disease or medical condition can reasonably be expected within 6 months1.
The Bill also specified that a treatment which only temporarily relieves the symptoms of a disease is not to be regarded as a treatment for the purposes of the definition. It also explicitly provides that a person is not to be regarded as terminally ill by virtue of only having a mental disorder or a disability (and specified definitions of these using existing legislation).
During the Bill’s progression through Parliament, the definition of terminal illness was amended in the following two ways:
Danny Kruger MP successfully moved an amendment to leave out “medical condition” from the definition of terminal illness. This was proposed to build stronger safeguards for disabled people into the Bill.
Naz Shah MP successfully moved an amendment to ensure that a person who does not meet the definition of terminally ill, cannot become terminally ill by voluntarily stopping eating or drinking or both.
The following issues were also discussed in the House of Commons, but did not result in changes to the Bill:
Requiring an illness, disease or medical condition to be specified in regulations, made by the Secretary of State, in order to be considered a terminal illness under the Bill.
Proposals for both shortening and lengthening the requirement for the person’s death to be reasonably expected within six months.
Adding criteria to the Bill that would stipulate when a disease or illness should not be characterised as terminal.
At the time of writing, the Bill has progressed to the House of Lords.3.
Lord Falconer's 2024 Assisted Dying for Terminally Ill Adults Bill1 defined someone as terminally ill if that person:
(a) has been diagnosed by a registered medical practitioner as having an inevitably progressive condition which cannot be reversed by treatment (“a terminal illness”), and (b) as a consequence of that terminal illness, is reasonably expected to die within six months1.
Lord Falconer withdrew his Bill following the introduction of Kim Leadbeater’s Bill.
Dr Allinson introduced the Assisted Dying Bill 20231 to Tynwald, the Parliament of the Isle of Man in June 2023 and was approved by the Isle of Man's Legislative Council on 25 March 2025. The Bill defined someone as terminally ill if that person:
(a) has been diagnosed by a registered medical practitioner as having an inevitably progressive condition which cannot be reversed by treatment (a “terminal illness”); and (b) as a consequence of that terminal illness, is reasonably expected to die within 12 months.
(2) Treatment which only relieves the symptoms of an inevitably progressive condition temporarily is not to be regarded as treatment which can reverse that condition1.
Under the definition of terminal illness, the Bill as introduced had a 6 month life expectancy criterion, which was amended to 12 months, in recognition that more people are living with terminal illness for longer as set out in the report of the All-Party Parliamentary Group (APPG) for Terminal Illness3. The APPG’s inquiry was designed to examine the impact of the six-month rule on terminally ill people’s ability to access benefits in 2019.
At its sitting on 21 May 2024 the States Assembly approved detailed proposals for assisted dying in Jersey1, and requested the Minister for Health and Care Jersey to bring forward primary legislation that permits assisted dying in Jersey for those with a terminal illness. The Draft Assisted Dying (Jersey) Law was lodged on 2 September 2025.
Article 2 of the draft law provides that an individual may be eligible for assisted dying if they meet the following health criteria (as well as a number of other criteria)
The health criteria are that the individual:
has a physical condition that is expected to cause their death within 6 months (or 12 months if the condition is neurodegenerative) i.e., it is a terminal illness; and
believes they cannot bear the suffering the condition causes them or is expected to cause them before their death, OR if treatment could extend their life, or make their suffering more bearable, they believe that they could not bear the suffering that the treatment would cause them2.
Including the current Bill, there have been four attempts to legislate for assisted dying in Scotland over the lifetime of the Scottish Parliament. The definitions used in the previous three attempts are as follows:
2004: Jeremy Purvis MSP’s Dying with Dignity consultation papersought to allow access to assisted dying if a person is “diagnosed with a terminal illness that will result in death within 6 months”1 . No further definition was included in the Bill.
2010: Margo McDonald MSP’s End of Life Assistance (Scotland) Bill, would have allowed a person to make a formal request for end-of-life assistance if that person “has been diagnosed as terminally ill and finds life intolerable; or is permanently physically incapacitated to such an extent as not to be able to live independently and finds life intolerable.”2 The following definition was included within the Bill:
For the purposes of subsection (2)(a) a person is terminally ill if the person suffers from a progressive condition and if death within six months in consequence of that condition can reasonably be expected.2
2013: Margo MacDonald MSP’s Assisted Suicide (Scotland) Bill would have allowed a person to make a request for assistance to end their life if that person has “an illness that is, for the person, either terminal or life-shortening, or a condition that is, for the person, progressive and either terminal or life-shortening”4 . No further definition was included in the Bill.
There are two models of eligibility for assisted dying around the world:
The terminal illness model, which allows people diagnosed with a terminal illness to choose to end their lives with medical assistance. There are usually specific conditions to be met and safeguards included in the legislation.
The unbearable suffering model, which is a wider approach. Here assisted dying or sometimes a form of euthanasiai is permitted for people who are experiencing unbearable suffering. This is not limited to those with a terminal illness.
Jurisdictions with a terminal illness model include Australian states, New Zealand and US states. Jurisdictions with the unbearable suffering model include Canada, Central and South America and Europe.
As the Assisted Dying for Terminally Ill Adults (Scotland) Bill follows the terminal illness model, this briefing examines definitions from legislation that follow the same model.
Assisted dying is currently legal in all six Australian States and the Australian Capital Territory. The Northern Territory is the only part of Australia which does not currently have an assisted dying law in place.
The definition used in assisted dying legislation is similar across Australia. The definition in most areas contains reference to a period of life expectancy of up to 6 months, or 12 months for a person with a neurodegenerative condition. The definition used in Queensland has a period of life expectancy, for all people, of up to 12 months. The definition used in the Australian Capital territory does not include a timescale..
The table below sets out the definitions of terminal illness used for eligibility across the six Australian States and the Australian Capital Territory:
| State | Definition |
| Victoria 1 | 9(1) For a person to be eligible for access to voluntary assisted dying—(d) the person must be diagnosed with a disease, illness or medical condition that—(i) is incurable; and(ii) is advanced, progressive and will cause death; and(iii) is expected to cause death within weeks or months, not exceeding 6 months; and(iv) is causing suffering to the person that cannot be relieved in a manner that the person considers tolerable. |
| Western Australia2 | 16(1) The following criteria must be met for a person to be eligible for access to voluntary assisted dying —(c) the person is diagnosed with at least 1 disease, illness or medical condition that —(i) is advanced, progressive and will cause death; and(ii) will, on the balance of probabilities, cause death within a period of 6 months or, in the case of a disease, illness or medical condition that is neurodegenerative, within a period of 12 months; and(iii) is causing suffering to the person that cannot be relieved in a manner that the person considers tolerable; |
| Tasmania3 | 6(1) For the purposes of this Act –relevant medical condition, in relation to a person, means a disease, illness, injury, or medical condition, of the person that –(a) is advanced, incurable and irreversible; and(b) is expected to cause the death of the person; and(c) except if the person is exempted from this requirement under subsection (3), is expected to cause the death of the person –(i) within 6 months; or(ii) if the disease is neurodegenerative – within 12 months.(2) For the purposes of this Act, a disease, illness, injury, or medical condition, of a person is incurable and irreversible and is expected to cause the death of the person if there is no reasonably available treatment that –(a) is acceptable to the person; and(b) can cure or reverse the disease, illness, injury or medical condition and prevent the expected death of the person from the disease, illness, injury or medical condition. |
| South Australia4 | 26(1) For a person to be eligible for access to voluntary assisted dying —(d) the person must be diagnosed with a disease, illness or medical condition that—(i) is incurable; and(ii) is advanced, progressive and will cause death; and(iii) is expected to cause death within weeks or months, not exceeding 6 months; and(iv) is causing suffering to the person that cannot be relieved in a manner that the person considers tolerable; |
| Queensland5 | 10(1) A person is eligible for access to voluntary assisted dying if— (a) the person has been diagnosed with a disease, illness or medical condition that—(i) is advanced, progressive and will cause death; and(ii) is expected to cause death within 12 months; and(iii) is causing suffering that the person considers to be intolerable; |
| New South Wales6 | 16(1) The following criteria must be met for a person to be eligible for access to voluntary assisted dying—(d) the person is diagnosed with at least 1 disease, illness or medical condition that—(i) is advanced, progressive and will cause death, and(ii) will, on the balance of probabilities, cause death—(A) for a disease, illness or medical condition that is neurodegenerative—within a period of 12 months, orEditorial noteSee subsection (2)(b) which provides that a person is not eligible for access to voluntary assisted dying merely because the person has dementia.(B) otherwise—within a period of 6 months, and(iii) is causing suffering to the person that cannot be relieved in a way the person considers tolerable,Subsection 16(2(b)(2) A person is not eligible for access to voluntary assisted dying merely because the person has—(a) a disability, or(b) dementia, or(c) a mental health impairment within the meaning of the Mental Health and Cognitive Impairment Forensic Provisions Act 2020. |
| Australian Capital Territory7 | 11(1) For this Act, an individual meets the eligibility requirements if—(b) they have been diagnosed with a condition that, either on its own or in combination with 1 or more other diagnosed conditions, is advanced, progressive and expected to cause death (the relevant conditions); and(c) they are suffering intolerably in relation to the relevant conditions;(2) However, an individual does not meet the eligibility requirement mentioned in subsection (1) (b) only because they have a disability, mental disorder or mental illness.(3) For subsection (1) (c), an individual is suffering intolerably in relation to their relevant conditions if—(a) persistent suffering (whether physical, mental or both) is being caused to them by—(i) 1 or more of the following matters:(A) the relevant conditions;(B) the combination of the relevant conditions and any other condition or conditions they have been diagnosed with (the other conditions);(C) treatment they have received for the relevant conditions;(D) the combination of treatments they have received for the relevant conditions and the other conditions; or(ii) the anticipation or expectation, based on medical advice, of suffering that will or might be caused by a matter mentioned in subparagraph (i); or(iii) a medical complication that will or might result from, or be related to, a matter mentioned in subparagraph (i); and(b) the persistent suffering is, in their opinion, intolerable.(4) In this section:advanced—an individual’s relevant conditions are advanced if—(a) the individual’s functioning and quality of life have declined; and(b) any treatments that are available and acceptable to the individual lose any beneficial impact; and(c) the individual is in the last stages of their life.condition means a disease, illness or other medical condition.disability—(a) has the same meaning as it has in the Discrimination Act 1991, section 5AA (1); but(b) does not include the meaning in that Act, section 5AA (2).mental disorder—see the Mental Health Act 2015, section 9.mental illness—see the Mental Health Act 2015, section 10.progressive—an individual’s condition is progressive if their condition is deteriorating and will continue to deteriorate. |
Assisted dying became legally available in New Zealand in November 2021 through the End of Life Choice Act 2019.
5(1) In this Act, person who is eligible for assisted dying or eligible person means a person who—
(c) suffers from a terminal illness that is likely to end the person’s life within 6 months; and
(d) is in an advanced state of irreversible decline in physical capability; and
(e) experiences unbearable suffering that cannot be relieved in a manner that the person considers tolerable; and
(f) is competent to make an informed decision about assisted dying.1
It also explicitly states that a person is not eligible if the only reason is that they are only suffering from any form of mental disorder or mental illness, have a disability of any kind, or is of advanced age.
5(2) A person is not a person who is eligible for assisted dying or an eligible person by reason only that the person—
(a) is suffering from any form of mental disorder or mental illness; or
(b) has a disability of any kind; or
(c) is of advanced age1.
The first review of the Act was undertaken in 20243. During that review, a recommendation (recommendation 10) was made to provide greater clarity about the time period during which a person can receive an assisted death under the Act.
Recommendation 10Add a provision that establishes a six-month period within which a person is able to set a date and receive an assisted death, following approval by the Registrar. This six-month period would commence from the date when the Registrar determines that compliance requirements have been met.Further, add a provision providing that an additional six-month extension of this period may be granted by the Registrar if at the end of the initial six-month period:
|
The Bill initially included a fixed six-month time-period for someone deemed eligible to set the date of their assisted death. Provisions were added later in the parliamentary process to allow a person to move the date up to six months beyond the chosen initial date. The report notes this may have been due to a concern that a six-month period would result in people choosing to have an earlier assisted death than planned, due to prognostic uncertainty. There was a worry that a person would need to make another application and risk losing competence to make an informed decision.
While this recommendation does not affect the eligibility of a person under the definition of terminal illness, it does allow for prognostic uncertainty. It recognises that the nature and speed of a person’s decline at the end of their life can vary and that some people may live for longer than six months but may still be experiencing suffering and be expected to die within a slightly longer period.
Medical aid in dying is currently authorised in 11 States and Washington, D.C. All States, and Washington D.C. use a definition that contains reference to a period of life expectancy of up to 6 months, except for Montana which instead states a “relatively short time”.
The table below sets out the definitions of terminal illness used for eligibility across these areas:
| State | Definition |
| California1 | 443.1. As used in this part, the following definitions shall apply:(q) “Terminal disease” means an incurable and irreversible disease that has been medically confirmed and will, within reasonable medical judgment, result in death within six months. |
| Colorado2 | 25-48-102. As used in this article, unless the context otherwise requires:(14) "terminal illness" means an incurable and irreversible illness that has been medically confirmed and will, within reasonable medical judgment, result in death within six months. |
| Delaware3 | 2502C. For purposes of this chapter:(17) “Terminal illness” means an incurable and irreversible disease, illness, or condition that as a medical probability, will result in death within 6 months. |
| Hawaii4 | 327L-1. As used in this chapter:"Terminal disease" means an incurable and irreversible disease that has been medically confirmed and will, within reasonable medical judgment, produce death within six months."Terminal disease" does not include age or any physical disability or condition that is not likely to, by itself, cause death within six months. |
| Maine5 | 2140.2. As used in this chapter, unless the context otherwise indicates, the following terms have the following meanings.M. "Terminal disease" means an incurable and irreversible disease that has been medically confirmed and will, within reasonable medical judgment, produce death within 6 months. |
| Montana6 | Montana has recognized a terminally ill patient's right to use prescribed life-ending medications through a court case, Baxter v. Montana. (354 Mont. 234 (2009).The District Court held that a competent, terminally ill patient has a right to die with dignity under Article II, Sections 4 and 10 of the Montana Constitution. The District Court concluded that Montana homicide laws are unconstitutional as applied to a physician who aids a competent, terminally ill patient in dying.Montana Code Annotated 2023TITLE 50. HEALTH AND SAFETYCHAPTER 9. RIGHTS OF THE TERMINALLY ILL ACT50-9-102. (16) "Terminal condition" means an incurable or irreversible condition that, without the administration of life-sustaining treatment, will, in the opinion of the attending physician or attending advanced practice registered nurse, result in death within a relatively short time. |
| New Jersey7 | C.26:16-3 Definitions relative to medical aid in dying for the terminally ill.“Terminally ill” means that the patient is in the terminal stage of an irreversibly fatal illness, disease, or condition with a prognosis, based upon reasonable medical certainty, of a life expectancy of six months or less. |
| New Mexico8 | Section 2. Definitions. —As used in the End-of-Life Options Act :J. "Terminal illness" means a disease or condition that is incurable and irreversible and that, in accordance with reasonable medical judgment, will result in death within six months. |
| Oregon9 | 127.800 §1.01.The following words and phrases, whenever used in ORS 127.800 to 127.897, have the following meanings: (12) "Terminal disease" means an incurable and irreversible disease that has been medically confirmed and will, within reasonable medical judgment, produce death within six months. |
| Vermont10 | 5281.As used in this chapter:(10) “Terminal condition” means an incurable and irreversible disease which would, within reasonable medical judgment, result in death within six months. |
| Washington D.C.11 | Sec. 2. Definitions. For the purposes of this act, the term:(16) "Terminal disease" means an incurable and irreversible disease that has been medically confirmed and will, within reasonable medical judgment, result in death within 6 months. |
| Washington12 | 70.245.010Definitions. (Effective until June 30, 2027.)The definitions in this section apply throughout this chapter unless the context clearly requires otherwise.(13) "Terminal disease" means an incurable and irreversible disease that has been medically confirmed and will, within reasonable medical judgment, produce death within six months. |