The HI-Point carbine could possibly be effective for self-defense, but it certainly wouldn't be my choice of pistol caliber carbine for that use, and I would not trust mine for that purpose for a number of reasons.
First as I said before, mine has not been sufficiently reliable. I have had at least the occasional failure to feed occurring with multiple magazines and with many different brands of commercial 9 mm FMJ ammo of different projectile mass, and I have not even tried to feed JHPs through it. I have contacted Hi-Point customer support multiple times regarding this issue, and messing around with the magazines has reduced the frequency of misfeeds, but not eliminated the problem.
Second, since I do not live in a state that decides how many rounds your magazine can hold, I find the limited capacity of the Hi-Point magazines unacceptable. The only other viable option is the Redball 20 round magazine. That does work reasonably reliably and won't void the warranty on the carbine. But being a single-stack magazine it sticks out way below the pistol grip and would be a big limitation if one had to shoot from prone and could make the carbine awkward to maneuver in tight quarters.
Third, the limitations imposed by the controls. I do not have small hands. But I find that when I have my shooting hand properly positioned on the pistol grip for good trigger control, accessing either the thin safety lever or the magazine release button requires shifting my grip with my shooting hand. The very thin safety lever might be quite difficult to find in a hurry in a tense situation. For me, these factors make this carbine a big no-no for self-defense. And if you were stuck having to buy the CA-compliant version with the egregious fin on the pistol grip, you would not be able to use either the safety lever or the magazine release lever with your right hand. Additionally, unless you modify the bolt by drilling and tapping a hole in it, you are pretty much stuck with the charging handle on the left side. That may suit a lot of people just fine, but not everybody. In addition, there are some funky little "shelves" within the magazine well, and I have found that if you try to insert a magazine quickly and have it angled much in a fore or aft direction it wants to hang up.
Now if you own a 995TS and have found it to be reliable, then I guess that is what you will use. But contrast this carbine with the Ruger PCC9. With the CA-compliant version of the Ruger, you would not be able to buy the threaded barrel and would be stuck with a 10 round magazine capacity. But you would be able to use reliable Glock magazines and would not have to deal with the ridiculous fin on the pistol grip. The charging handle is reversible from the right to the left side, and you can even buy an aftermarket charging handle and have one on both sides if you wish. The safety lever is very easy to disengage for a right-handed shooter while maintaining a proper grip and magazine changes are smooth. The magazine release button is reversible. It is not situated in a location where it can be accessed with the thumb, but there are several aftermarket options for an extended magazine release button that makes it very easy to find and depress. And if you live in most states, you can use readily-available magazines from Glock or Magpul that hold up to thirty rounds, yet stick out less far than the 20 round Redball magazine for the Hi-Point. So the odds of having to change magazines in a self-defense scenario become much smaller.
Just some considerations for people who might not have first hand experience with either of these pistol caliber carbines who are considering buying one, and might possibly foresee the need to rely on it for self-defense purposes.