Referral from the doctor treating the terminal illness, from the psychiatrist who can say the person is of sound mind and from the person's own GP would not be sufficient checks and balances to ensure that the person really does want to die?

Now, I'm sure there could be some nefariousness and it could be abused, but that happens now under the term "pain management"; because euthanasia is already underground it makes abuses all the more harder to find.