Ok. So you don not understand that that's the whole point of the case? If he is credited and is proven that he should have credited Wilcock he would have to pay a handsomely sum of money.
Oh and by the way, in a trial it doesn't matter you prove that you have written 10000 songs, you have to prove you wrote the one's that are being challenged or at least, as I have said before, present reasonable doubt that (in this case) Wilcock DID NOT wrote them... Let me ilustrate you further:
When Hallowed came into the light (it was played in the soundcheck before Maiden played under the moniker Genghis Khan) Steve had presumably written 15 songs by himself and at least 6 songs with other people (Di'Anno & Murray), however, he "presumably" lifted lyrics (which means he wasn't able to write the song completely by himself) from a song he didn't write although he has been credited as the only writer of it.
As you can see, the whole matter presents a reasonable doubt that maybe he didn't write ALL the lyrics to a song in which he is credited as the sole writer. It doesn't matter if it is two lines or a whole verse, is just means that you didn't write the entire song