This is not a trick question. There are some Christians who believe they are no longer sinners when they came to Christ. Let's analyze and find out from God's Word what happens to our sins when we repent and believe the gospel.
Ephesians 1:7 tells us that In Christ we have redemption through His blood, the forgiveness of sins, according to the riches of His grace. The word forgiveness in the Greek is Aphesis. It means remission, to release sins from the sinner. One must understand that when Jesus took away our sins through His death, He was our substitute. He acted as our intercessor and mediator; He suffered, was punished by the Father for our trespasses and paid our sin debt when He died. This was a judicial act by Christ.
If one can imagine a court scene:
The Judge is the Father, Satan is mankind's accuser, and Jesus is our defense attorney, our advocate. Now the devil of course wants us to kill us so that we're sent to hell unforgiven so he begins to belch out all of our sins to the Judge: Idolater, murderer, liar, glutton, drunkard, thief, adulterer, blasphemer, covetousness, etc. The Judge says to the defense attorney, "What do you have to say about these accusations?" The defense replies to the Judge, "My Lord the things the accuser has charged my clients with were true, but my Lord You sent Me here not only to defend my clients, You commanded Me to give My life for them because You and I love them. I did what You commanded Me 2,000 years ago and those that have repented and put their trust in Me I cleansed with my blood and saved them so the enemy has no right to them. They belong to You and Me My Honorable Lord. I AM their redeemer. I AM their Savior!
Because of Christ we have received a divine pardon. The Judge has banged His gavel and given us a not guilty verdict. We are free in Christ. Praise God! But just because our sins are no longer counted against us, it does not mean we are not still sinners - we are. How do I know this?
The apostle John in I John 1:8-10 says this to believers, "If we say that we have no sin, we deceive ourselves, and the truth is not in us. If we confess our sins, He is faithful and just to forgive our sins and to cleanse us from all unrighteousness. If we say that we have not sinned, we make Him a liar, and His word is not in us."
So, if we have been forgiven of all our sins when we initially repented and believed in the atoning work of Jesus for salvation, then why does John say as believers that we have to confess our sins to be cleansed from unrighteousness? I can understand why John's words could be confusing. Were our sins washed away or not?
You see Jesus delivered us from the penalty and power of sin, but currently not its presence. Our bodies have not received its glorification yet so we still struggle in our flesh and war against sin. Because the temptation to sin is with us, we fall prey to sin and we must confess it to the Lord for ongoing cleansing. This confession of sin is not forgiveness so that we can be saved again, but rather a familial or relationship forgiveness - like a father would give to his son that disobeys him (Hebrews 12:5-11).
I John 2:1-2 says, "My little children, these things I write to you, so that you may may not sin. If anyone sins, we have an Advocate with the Father, Jesus Christ the righteous. And He Himself is the propitiation for our sins, and not for ours only but also for the whole world."
Notice what the Elder Apostle John said, my little children. He is clearly making reference to Christians; meaning we do sin. Now, sinning cannot be the pattern of the believer's life because we have been delivered from it. It no longer has dominion over us. You see, we sin, but we must not practice it. That was our former pattern of life.
Why we should continually confess our sins
Paul said in Romans 15:4, "For whatever things were written before were written for our learning, that we through the patience and comfort of the scriptures might have hope."
God relayed clearly to the children of Israel that in order for Him to dwell in their presence, the land could not be defiled by their sin. How in the world could approximately a couple of million people remain clean? By slaughtering animals, shedding their blood as a sin substitute for them. God required usually sheep, lamb, goats and bulls without blemish to be a sacrifice. The blood shed from these animals was an atonement for the sins of the people. The reason they had to continually offer sacrifices was because the animal's blood could only cover sins, it could not wash away the sins of the people. Hebrews 10:4 tells us the blood of bulls and goats could NEVER take away sins. The blood of animals pre-figured the once and for all sacrifice of Jesus Christ. Remember the words of John the Baptist, "Behold the Lamb of God who takes away the sin of the world" (John 1:29).
I provided that small history lesson to show that although we are clean by the blood of the Lamb inwardly, our outward man which Paul describes as a body of death is not clean and is subject to sin (Romans 7:24). Ongoing confession of sin is good for our soul and body. It is not something we should do ritualistically or mechanically. Rather, we should do it humbly and joyfully realizing that we never deserve the right to even dwell in the presence of the Lord, let alone approach His holy majestic throne.
So yes, we are still sinners, no question about it. The difference for the believer vs. the non believer is that our lives can no longer be dominated by it. The power of the Holy Spirit compels us to resist sin. The Bible tells us that we cannot practice sin because of the indwelling Holy Spirit (1 John 3:4-9). Notice I did not say temptation for we are always tempted due to the corruption that is in our flesh and the sinfulness of others.
There will come a glorious day when we will sin no more. That will be when we are glorified in our bodies. That blessed day is when Jesus returns for His Bride the Church. The dead in Christ will rise first. Then all those who are alive will be changed and will meet the Lord in the air (1 Cor 15:51-58; 1 Thess 4:13-18).