I am wondering whether leather is halal or haram if the animal dies or is killed in the wrong way? I got a couch that was made of leather, I took it but I did not want it in the house or to be sat on because I think it is haram.
The prohibition on maitah (dead meat) is explicitly in regards to eating it, not on using its leather for other purposes. There are a number of sahih ahadith regarding the hides of dead animals, where the prophet is reported to have permitted their use, such as this one:
The above indicates that even if an animal dies or is killed in a manner which would render its meat haram, the hide itself — insofar as it is not eaten, as couches typically aren't — remains permissible.
While some variations on the above hadith include a condition that the hide be tanned before using it, they remain inconsistent on this point. However, there is a more general hadith, also sahih, which clearly indicates that hide is purified by the process of tanning:
This still doesn't indicate whether rawhide (i.e., untanned leather) is permissible, but it does reinforce the idea that leather from maitah, if it is tanned, can be used.
(As an aside, I've read claims that God commanded Musa to remove his shoes in the valley of Tuwa (Qur'an 20:12) specifically because they were made of untanned leather; I can't speak for their authenticity, but it's worth noting.)
Also, while the general meaning of the tanning hadith suggests that all hides become pure after tanning, there is disagreement among the scholars whether this would actually apply to hides which are inherently impure (e.g., pigskin), or if it only applies to those which would otherwise be permissible to eat if they weren't maitah.
In conclusion, as long as the couch is made of tanned cow leather (which, as far as I know, most leather couches are) I know of nothing which would prohibit it's use. If it's made of untanned leather, or pig leather, there is some dispute as to it's permissibility; in lieu of any strong evidences to the contrary, my personal opinion is that they would remain permissible, although not preferable.
There are many hadiths in which the prophet says that tanning an animals skin (the process in which leather is made) makes an animals skin pure.
But there is also a wide range of views on this hadith by the different schools of thought.
The Hanafi school of thought states that it purifies all animal skins exept that of a pig.
The Shafi'i school of thought states, that in addition to pigs being nijis regardless of tanning, dog's skin too cannot be used even after tanning. The severity of its impurity is established by the fact that the Prophet (peace be upon him) ordered us to wash a dish seven times, once with soil, if a dog drinks from it, as this hadith mentions:
The third opinion is held by some scholars that tanning can only be used on animals its lawful to eat if they were slaughtered correctly. This is based on the wording of the hadith "tanning is as slaughtering them"citation needed it is argued that if tanning is as slaughtering an animal then tanning somthing such as a tiger still wouldn't be halal since is wouldn't be halal by simply slaughtering it. This means that only dead cows, sheep, camels, and other food animals can be purified by tanning them.
And the last, and very weak opinion is that no animals flesh can be purified by tanning. This is based on weak ahadith in which the prophet says: “Allah’s Messenger (peace be upon him) prohibited the use of the sinew and hide of an animal that dies (without being slaughtered).” Ibn `Abd al-Barr says about this hadîth that its chain of transmission is not strong. This last view would also mean that the weak hadith would contradict the stong one, which means that one must be incorrect, and most likley its the weak one.