Wait so is it standard practice to look for CP in all sex offense cases or are we just conjecturing if it comes up during a device search?
Let me break it down for you:
Criminals are on the whole exceptionally dumb. Most of the ones who aren't dumb are impulsive, which can be just as bad or much worse. If you are intelligent or calculating, you probably don't get caught. You selected your victims for a reason, you avoided unnecessary risks, you stayed off the radar. The exception is dumb luck, shit, look at how Timothy McVeigh got caught.
The second a sex offense acquires an electronic component securing a search warrant becomes almost trivial. Did he text the victim? Did he threaten the victim or their guardians or family? Did the victim text him? Did he use WhatsApp or facebook or similar? Did he solicit on instagram, tiktok, or the like? Did the victim attempt to add him on social media? Did you find receipts or labels for questionable items like loli onaholes or the like that were ordered online recently?
Consider also the nature of sexual crimes. The offender will reassure the victim, even if the initial offense was by force. The offense may be largely or completely consensual (even if the victim is not of age or unable to legally consent) Some children and teens will enjoy the sensation or believe it to be pleasurable. They will correspond with the offender, and often not in nearly so careful terms as to preserve his identity or the nature of their acts. The offender will encourage them to be quiet, or not disclose what happened. He will use evasive language. He may offer to buy them off. What he will NOT do is ignore them. He can't; unless he kills the kid they will talk about it or discuss it. He has to emphasize to them that it's their secret, and to definitely not let mom know. Because guess what, as soon as Mom finds out, she brings it to the cops, and they don't need a warrant for the victim's phone when mom willingly gives the cops a phone full of suggestive messages that may give them plenty of probable cause on their own.
All of those create a good reason to inspect his computer and/or phone. As for the majority of people the computer and phone share search history, cloud storage, and many accounts one will often lead to the other. And while you can recover destroyed or wiped drives in many cases, most offenders just leave it "laying around". I've found questionable photos as the desktop background (barechested old man handling a child, set to the "tiled" orientation, if you want a mental image). Most of the time it's in a folder with a relatively innocuous name and you don't need advanced training in computer forensics to locate it. Only rarely are computers passworded. Even if they are, sometimes the offender will give it to you, thinking his efforts to hide his indiscretions will be effective. Failing that he wants to play the "I didn't know that was there, it must have been a hacker or virus" excuse due to how incredibly obvious it was. If he is married or lives with his parents, they will often give you the password. A majority of the time the recently used files section will get you to the folder. If that doesn't you'll find something in their search history. Literally open their browser and type a letter in the google search box. Start with "C" and look at the suggestions that it puts up or the past searches. Major keywords will be rape, porn, child, kids, children, jb, jailbait, the like. Expect it to be interspersed with searches about what is the darkweb and what is Tor. You can search their history but some of them wipe that, even though that's only a slight inconvenience. Lots don't know you have to empty the recycle bin. The cop already requested a preservation order with Apple, Facebook, Instagram, Snapchat, Tiktok, and everything else right before you knew the heat was on and possibly before he had the search warrant.
The countermeasures that 99% of them take are totally mundane. Most criminals are not intellectually or technologically advanced. Formatting a drive if they don't physically destroy it is about all they will do. Many don't know what the individual parts do; I've seen disk drives and monitors destroyed in an attempt to prevent discovery, presumably born from a belief that those were the hard drives. Thermite dead man switches and magnet hard drive wipers? They might be out there, but not for most pedos.
It doesn't have to be from a focused attempt to find child porn specifically, but it's incredibly easy to find incidentally, and very common even if the initial offense wasn't child related. Unless someone is incredibly fixated on a particular fetish or kink, it is highly likely that the sexual proclivities of anyone willing to commit sex crimes will branch out into the more obscene and prohibited material. They very likely took photos of their victim at some point if not the actual event itself. More than one sex offender has been hung by simple exif data. Even poorly focused pictures of preteen tits make a decent impact in an interview when you point out that they were taken by a phone that is exactly the same as that owned by their victim on the date of a suspected offense...
The long and convoluted point is that getting a reason and cause to secure a search warrant for a phone and/or computer nowadays is almost braindead. And a sicko will do sicko things. Do I think Chris' computer is absolutely loaded down with cheese pizza? Probably not, but I think there is a very high likelihood that something like that may be found just based on his sexual immaturity, entitlement attitude, and the fact that he was sexually deprived and depraved enough to rape his own mother. Wherever his line is drawn, if he can fuck an 80 year old he will probably get a stiffy to a little kid too, especially if "sexualized". He is just too similar to too many I've seen just like him, when you remove the CwCville veneer anyway.
The specificity of the warrant does not have to be that great due to the lack of countermeasures employed by offenders. You are likely to find compromising material incident to a casual search... which leads to more and more. Renaming extensions to render files temporarily unusable is not a rare strategy for offenders either. All the more reason to check fishy entries. If they are on probation or parole, all the better- you get free reign without any strings attached or even needing a warrant.
Obviously rules and laws governing searchea vary greatly by jurisdiction. Electronic search law is still very much a developing area.