Concept:
Euthanasia means ending life or allowing life to end in order to relieve suffering.
On the basis of consent, euthanasia may be:
\[
\text{Voluntary}
\]
\[
\text{Involuntary}
\]
\[
\text{Non-voluntary}
\]
Step 1: Check voluntary euthanasia.
Voluntary euthanasia takes place when the patient gives clear consent.
In the question, the patient is an infant or is in coma.
Such a patient cannot give consent.
So, it is not voluntary euthanasia.
Step 2: Check involuntary euthanasia.
Involuntary euthanasia takes place when euthanasia is done against the will of the patient.
Here, the patient has no capacity to express will.
So, it is not involuntary euthanasia.
Step 3: Check non-voluntary euthanasia.
Non-voluntary euthanasia happens when the patient is unable to give consent.
Examples are:
\[
\text{infants}
\]
\[
\text{coma patients}
\]
\[
\text{patients without decision-making capacity}
\]
This exactly matches the question.
Step 4: Check passive euthanasia.
Passive euthanasia means withdrawal or withholding of treatment.
But the question says:
\[
\text{administering a lethal injection}
\]
which is an active act.
So, passive euthanasia is not correct.
Hence:
\[
\boxed{\text{Non-voluntary euthanasia}}
\]