Hybrid/Humans

He used to be the only human-synth hybrid, then was believed to have become fully human when the synthetic components in his brain were removed, but it was actually revealed that his synth blood, mixing with his human blood, altered his DNA, inscribing the synth gene in it and allowing him to pass it on to his daughter. This means that he’s still part synth.
As a human-synth hybrid, Leo has a slightly different physiology from most humans and this gives him a set of synth skills different from humans. He also has abilities unrelated to his hybrid physiology.
Non-Hybrid: These abilites are unrelated to his hybrid physiology.
Computer Expert: Leo is an expert with computers, as he is able to set up complicated programs to scan for traces of synth programming. He was also able to track where Mattie posted from.
Hybrid: These abilites come from Leo being a hybrid.
Digitized Memory: Most of his memories are digitized, which means he cannot forget anything, but he can also upload and play them back on a computer or presumably other electronic devices with the same capabilities.
Charging: He has a wire in the left side of his abdomen that allows him to charge when plugged into a socket. It also accelerates his healing, though this could mean Leo always has accelerated healing like the other synths, but he just needs extra electrical energy because he's a hybrid and he doesn't run completely on electricity. Charging does not replace food and water, those are still necessities for him while charging may not be.
Mental Link: Leo is able to link with the other sentient synths to access the program left by his father by going into a trance-like state. It is unknown if this link can be used in other ways.
* The memory of his mother playing peek-a-boo to him is his most played back memory.
* According to Fred, when he was younger, he loved to collect dead leaves.
* Three years before the show began, Leo allegedly was a Junker, along with Salim Sadik. He even bailed him out of jail, when Salim was arrested for illegally modding Synths.
* Leo's Headcrack forum name is: User885
* Both of his parents committed suicide, though at different times and for different reasons.
* In Season 2, we learn that the base Leo and the Elster's have set up, is somewhere between Hemel Hempstead and St. Albans, in Hertfordshire.
* He was initially part human and part synth due to the synth components added to his brain to save his life. Then Hester stabbed him in the back of his head and those synth parts were damaged and consequently removed. This led everyone to think he was fully human again, even if he healed surprisingly fast, without any kind of brain damage, and was much stronger than expected. It was revealed in the Season 3 finale, that his synth blood and his human blood had mixed, altering his DNA and somehow infusing it with synth genes, which are now an integral part of his genetic code. This confirms that Leo is still partly synthetic, and that his synth genes were transmitted to his daughter with Mattie, who is confirmed to be half-synth and half-human as well.