Can you attack a specific creature while blinded during combat?

Question

When a character is blinded, they suffer the following drawbacks:

A blinded creature can’t see and automatically fails any ability check that requires sight. Attack rolls against the creature have advantage, and the creature’s Attack rolls have disadvantage.

Given that these seem to be the only restrictions you have while blinded, would it be possible to determine an individual creature's location and identity (to ensure you're not attacking your allies) by using your other senses? This question also applies to combat in a heavily obscured environment. I can't seem to find any concrete rules about this type of situation.

Answer 1

Yes, you can.

Using the following rule which should also apply when you are Blinded (PHB p. 194):

Unseen Attackers and Targets

Combatants often try to escape their foes’ notice by Hiding, casting the Invisibility spell, or lurking in Darkness.

When you attack a target that you can’t see, you have disadvantage on the attack roll. This is true whether you’re guessing the target’s location or you’re targeting a creature you can hear but not see. If the target isn’t in the location you targeted, you automatically miss, but the GM typically just says that the attack missed, not whether you guessed the target’s location correctly.

When a creature can’t see you, you have advantage on attack rolls against it. If you are hidden—both unseen and unheard—when you make an attack, you give away your location when the attack hits or misses.

Additionally, other characters can perform a Help action to give you advantage in your turn, which would offset the disadvantage above. This could be regarded as shouting directions to you, maneuvering a creature towards you, etc.

Also, characters have what are essentially Free actions (Other Activity on Your Turn, PHB 190) on their turns, which can include speaking a few words. A DM could rule that calls of 'Foe to your left,' 'Two ten feet in front,' or 'I'm right behind you,' would help a Blinded character avoid friends and only attack enemies, albeit still with disadvantage unless given Help. Otherwise, they should have some chance of striking a friendly target, especially if everyone is clustered together in a wild melee.

Answer 2

Usually yes, but sometimes no.

You can usually still make attacks against specific creatures, but it may depend on your perception to know where they actually are. Please note that creatures are not hidden from you just because you are Blind. Unless they take the hide action, they are simply unseen.

Melee attacks: yes

A Blinded creature may make a melee attack against an unseen creature if it knows or can guess what square it is in. You'll have disadvantage on the attack roll unless you are otherwise granted advantage (such as if the target is also Blind). Note that grapples don't have an attack roll and so you wouldn't actually be at a disadvantage.

Ranged attacks: probably yes

A Blinded creature may make a ranged attack against an unseen creature if it knows or can guess what square it is in. It may be much more difficult to aim properly as distance increases though. Some DMs might not allow this at all, while some might increase the difficulty of such an attempt. You'll have disadvantage on the attack roll unless you are otherwise granted advantage (such as if the target is also Blind).

Spells: depends on the spell

Some spells require that you be able to see your target. (Most spells require line of effect, which should not be affected by being Blind.) Casting a spell in a location where there is no enemy (bad guess=invalid target) will waste your spell slot and do nothing. Spells with saves work a little better, since you don't suffer disadvantage since there is no attack roll. Area spells can also be effective since you are more likely to catch your target in the area.