Grammar question - I think it relates to plural or singular

Using the plural pronoun to refer to a single person of unspecified gender is an old and honorable pattern in English, not a newfangled bit of degeneracy or a politically correct plot to avoid sexism (though it often serves the latter purpose). People who insist that “Everyone has brought his own lunch” is the only correct form do not reflect the usage of centuries of fine writers. A good general rule is that only when the singular noun does not specify an individual can it be replaced plausibly with a plural pronoun: “Everybody” is a good example. We know that “everybody” is singular because we say “everybody is here,“ not “everybody are here” yet we tend to think of “everybody” as a group of individuals, so we usually say “everybody brought their own grievances to the bargaining table.” “Anybody” is treated similarly.


However, in many written sentences the use of singular “their” and “they” creates an irritating clash even when it passes unnoticed in speech. It is wise to shun this popular pattern in formal writing. Often expressions can be pluralized to make the “they” or “their” indisputably proper: “All of them have brought their own lunches.” “People” can often be substituted for “each.” Americans seldom avail themselves of the otherwise very handy British “one” to avoid specifying gender because it sounds to our ears rather pretentious: “One’s hound should retrieve only one’s own grouse.” If you decide to try “one,” don’t switch to “they” in mid-sentence: “One has to be careful about how they speak” sounds absurd because the word “one” so emphatically calls attention to its singleness. The British also quite sensibly treat collective bodies like governmental units and corporations as plural (“Parliament have approved their agenda”) whereas Americans insist on treating them as singular.

I've been struggling with this for a long time. I wanted to write this instead:

...... So after "Lifers" have served their minimum sentences, they can apply for release on parole, and if successful, will be permitted to serve the remainder of their life sentences in the community.

However, I'm not sure whether I should be speaking about all Lifers or just an individual Lifer. The second paragraph where I use "Lifers" sounds better to me, but for some reason it seems wrong to be.

Hi All: I was hoping that somebody could answer a question I have. I think it relates to whether something is singular or plural, but I don't know for sure.

Here is a paragraph that I wrote. Is my writing correct when, in the second sentence, I use "Lifer" and "he or she", and in the third sentence "their" and "they".

The mandatory sentence for first and second degree murder in Canada is Life, with a varying number of years that must be served before a person is eligible for parole; usually between 10 and 25 years. So after a Lifer has served their minimum term of imprisonment, he or she can apply for release on parole. If their application is successful, they will be permitted to serve the remainder of their life sentence in the community.

"A shortcoming that the studies I just mentioned have in common is the absence of a comparison group of other ex-prisoners to which the exonerees can be compared."