Concept:
Euthanasia can be classified according to consent.
The main types are:
\[
\text{Voluntary euthanasia}
\]
\[
\text{Involuntary euthanasia}
\]
\[
\text{Non-voluntary euthanasia}
\]
Step 1: Understand voluntary euthanasia.
Voluntary euthanasia occurs when the patient clearly gives consent.
In the question, the patient is an infant or in coma.
So, the patient cannot give consent.
Therefore, it is not voluntary euthanasia.
Step 2: Understand involuntary euthanasia.
Involuntary euthanasia occurs when euthanasia is done against the patient's will.
Here, the patient has no ability to express will.
So, it is not involuntary euthanasia.
Step 3: Understand non-voluntary euthanasia.
Non-voluntary euthanasia occurs when the patient is unable to give consent.
Examples include:
\[
\text{infants}
\]
\[
\text{patients in coma}
\]
\[
\text{patients permanently unable to decide}
\]
This matches the question.
Step 4: Check passive euthanasia.
Passive euthanasia means withdrawing or withholding treatment.
But the question mentions administering a lethal injection, which is an active act.
So, passive euthanasia is not correct.
Hence:
\[
\boxed{\text{Non-voluntary euthanasia}}
\]