I think it depends upon what the topic is whether Hamas lies or not.
Pajamas Media » Hamas’ Lies about Gaza Fatalities Unmasked
Hamas: Lies, Secrets, Torture, Murder, and Intimidation :Italy | NowPublic News Coverage
Rhymes With Right - Gaza Doctor: Hamas Lies About Civilian Deaths!
All I did was type "Hamas" and "lies" into google's search bar.
L Gilbert's post above references weblogs and forums like this, but since those posts reference the Ynet News, Jerusalem Post and the IDF, I'll accept the references as reliable as the original sources.
I can't read Italian, but that source appears to reference a statement by an unamed Gaza doctor who won't identify themself out of fear therefore an unverifiable opinion.
The other posts are based on the difference between IDF and Hamas claims about the ratio of militant to civilian casualties. The main reason for the differnce comes from their different definitions.
...At a news conference Wednesday, Sarah Leah Whitson, executive director of the Middle East and North Africa Division of Human Rights Watch, said Israel had attacked police stations in Gaza on the ground they were "combatants".
"Police were not combatants and could not represent legitimate targets unless actively engaged in hostilities," she pointed out. "It was Israel's burden of proof to show the police they targeted were, indeed, Hamas militants."
Instead, she said, it appeared that Israel had targeted police stations on a "blanket basis".
Whitson said that only combatants actively engaged in fighting were legitimate targets of Israeli attacks.
Thus, a Hamas official at the Ministry of Health was not a legitimate target and neither was a Hamas media broadcasting station....
Aid Groups Dispute Israeli Claims in Gaza Attacks | Asian Tribune
Israel: Transforming International Law by Violating It
by George Bisharat
...In the Gaza fighting, Israel has again tried to transform international law through violations. For example, its military lawyers authorized the bombing of a police cadet graduation ceremony, killing at least 63 young Palestinian men. Under international law, such deliberate killings of civilian police are war crimes. Yet Israel treats all employees of the Hamas-led government in the Gaza Strip as terrorists, and thus combatants. Secretaries, court clerks, housing officials, judges - all were, in Israeli eyes, legitimate targets for liquidation.
Israeli jurists also instructed military commanders that any Palestinian who failed to evacuate a building or area after warnings of an impending bombardment was a "voluntary human shield" and thus a participant in combat, subject to lawful attack. One method of warning employed by Israeli gunners, dubbed "knocking on the roof," was to fire first at a building's corner, then, a few minutes later, to strike more structurally vulnerable points. To imagine that Gazan civilians - penned into the tiny Gaza Strip by Israeli troops, and surrounded by the chaos of battle - understood this signal is fanciful at best.
Israel has a lengthy history of unpunished abuses of international law - among the most flagrant its decades-long colonization of the West Bank...
Israel: Transforming International Law by Violating It | CommonDreams.org
So no I don't buy IDF accusations that Hamas is lying about the ratio of civilians to militants, nor do I accept the IDF definition of who is a militant, civilian or human shield. I'll go with the Hamas definition, which is based on international law.