For this trophy you need to gain one Silent Assassin Rating, the trophy will pop during the end-of-level Statistics screen. At the end of each mission you get awarded a rating which is measurement of your performance in that particular level. The Silent Assassin Rating is the best Rating you can obtain in the game. When you complete a mission you will see a stat screen; on the right-hand side there is an 'Aggression Bar' this has to be virtually empty and just above it there is a 'Stealth Bar' this has to be pretty much full in order to achieve a Silent Assassin Rating.
Note: The timing you complete a level in; the difficulty that you play the game on and the amount of in-level saves you use will not affect your end-of-mission rating. Ideally you want to complete a level without any alerts, kills, shots fired and this will practically guarantee you a Silent Assassin Rating. Here are some conditions which are paramount if you want to achieve this rating:
You can only kill the targets that you have been contracted for. You will know exactly who your targets are by pressing which will activate the map, they are represented as the Red Circle. You cannot kill any innocent people, you can however knock them out with your Syringe. You are permitted to kill only one guard, guards are illustrated as the Orange Circle on your map. Naturally you would think that if someone is carrying a gun then they are a guard, this is not always true. For example in Mission 7: Traditions of the Trade the armed security officers are actually recognised as innocents, therefore if you were to kill one this will stop you from getting the rating. Just bare this in mind if you intend on killing someone.
If you use a Firearm to kill your target, it must be a clean shot. By clean shot I mean you must shoot them directly in the head which will deliver a fatal blow with just one bullet. You can not shoot multiple times. As after three shots this will effectively end your chances of getting the rating. You can use Melee Weapons to take your target out. Providing you do not get spotted then this is fine. Poisoning, drowning or using pillows to take your target out is also fine.
At the top of the screen you get little alerts in Red writing. You are allowed only two of these if you receive any more then this will prohibit you in getting the rating. Alert messages range from: 'Your cover has been blown' 'Nearby guards have been alerted' and 'Guards have found a dead/unconscious person'. Just to clarify, you must receive no more than two of the alerts mentioned above within a mission otherwise you will not get the Silent Assassin Rating.
You must not receive no more than one close encounter. A close encounter is when your cover gets blown either from a guard, target or civilian/VIP.
You do not have to finish missions in your suit, completing a level in another disguise will have no affect on your end-of-level rating.
There are some exceptions to the rules of the rating in Missions 3 and 6: The Bjarkhov Bomb and Deadly Cargo respectively. In The Bjarkhov Bomb you have to blow up a submarine, this will cause 3 or 4 soldiers to die as a result. However a pardon is granted and it will not count towards your end-of-level statistics. The same also applies in Deadly Cargo. If you do not extract quickly enough after completing your objects, then the SWAT team will launch an assault on the ship thus killing numerous guards.
It is by no means easy to get a Silent Assassin Rating, you can do everything perfectly up to and including extraction, only for the alerts come flooding in. There is an art to it, it may well be the case that you will have to redo some levels a few times in order to grasp the perfect route to ensure you can dance your way through them from start to finish without being spotted by the guards. Here some tips and factors that you may well want to take into account when trying to earn this rating.
Get a disguise and maintain your Cover
It is generally the case that you can not complete a mission just in your suit, most of the time you will reacquire a disguise in order to pass through places smoothly. To acquire a disguise you may have to knock out/kill a guard or sometimes there is a change of clothing just lying around to be changed into. Once you have your disguise it is vital that you maintain your cover. If your cover gets blown then realistically your chances of getting a Silent Assassin rating are gone along with it, this is because every guard within the compound tends to rush over and investigate. Keeping your disguise is relatively simple, refrain from making any erratic movements such as running and stopping or zig-zagging in opposite directions as this causes suspicion and, depending on what difficulty mode you're on, your cover could get blown as result.
Passing guards who have the same disguise can be a bit hairy but it is doable. Walk with conviction, do not delay, walk straight pass, do not touch them and nine times at of ten you will be fine. Sometimes the game can randomly glitch on you and you will get caught, but there is nothing you can do about it really. Lastly the music will sometimes change so don't worry as this does not mean you have been spotted but you are practically on the verge of being so.
Syringe and Fibre Wire
In every mission you have a Syringe at your disposal. The affect of this is, if used correctly, you can knock somebody out for around 7 minutes. Which is great for getting disguises or bypassing a vigilant guard/civilian who is obstructing your pathway. The main advantage is that it does not have a fatal outcome and therefore it will have no affect on your rating. However this can be a double-edged sword because the person who you knocked out can regain consciousness and be a complete hindrance. What usually happens is he will run, alert the nearby guards and then they will be looking for somebody suspicious in the disguise that you have just taken. However if you do not take his disguise he will just wake up and continue like nothing has happened. Another drawback is that it takes 5-8 seconds to administer a full dose, which can arouse a few problems. For example a guard or a civilian could walk by and spot you.
The Syringe is a great short term solution if you are confident in taking your victim's disguise, hiding his body and are able to complete the level's objectives quickly but as a long term solution, as discussed above, you can encounter some problems especially in the longer levels where it takes time to complete.
An alternative to using the Syringe is the Fibre Wire, like the Syringe you start with it in every mission. It is one of 47's trademark weapons (the other being the Silverballers) and unlike the Syringe it deals with your opponent instantly. Providing you hide the body well then you can have no worries. However its main drawback is that it has a fatal outcome so use this tactic in moderation. The way you use the Fibre Wire is very much the same as you would use the Syringe, sneak up to someone and from behind press . If you need to know how to use the syringe then see Sleep Well.
This is only applicable if you are playing the game on Normal or Expert Difficulty but by pressing it will show you a map and it is a live monitor of the movements of every single person in the level. Furthermore it shows points of interest which can be disguises or Poison and so on. This feature is invaluable and it allows you to plan your routes through every level perfectly, because sometimes when trying to kill your target the last thing you want is a guard walking in on you. Lastly it also informs you of where the exits are which is the last thing you should do after finishing that level's objectives.
Note: When playing on Professional Difficulty you will still get the map feature however it only shows the whereabouts of your target, points of interest and extraction points.